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Vol. 24, No. 2, 2014, Nuclear Physics News 1

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2 Nuclear Physics News, Vol. 24, No. 2, 2014

NuclearPhysicsNews

Cover Illustration: Pb-Pb collision in the ALICE detector (see article on page 13).

Volume 24/No. 2

ContentsEditorialNuclear Physics for Medicine

by Maria José Garcia Borge ....................................................................................................................... 3

Feature ArticlesBeyond the Neutron Drip-Line

by Thomas Aumann and Haik Simon ........................................................................................................... 5The Cosmological Constant Puzzle: Synergies with Nuclear Physics and its Measurement in Astrophysics Experiments

by Steven D. Bass......................................................................................................................................... 10

Facilities and MethodsRecent Results from the ALICE Collaboration

by Elena Bruna ............................................................................................................................................ 13Multi-Reflection Time-of-Flight Mass Separation and Spectrometry

by Susanne Kreim, F. Wienholtz, and R. N. Wolf ......................................................................................... 20

Impact and ApplicationsSome Physical Issues of the Thorium Molten Salt Reactor Nuclear Energy System

by Hongjie Xu, Zhimin Dai, and Xiangzhou Cai ......................................................................................... 24

Meeting ReportsThe Fourth International Particle Accelerator Conference

by Zhentang Zhao ........................................................................................................................................ 3110th Latin American Symposium on Nuclear Physics and Applications

by Oscar Naviliat-Cuncic ............................................................................................................................ 32Shape-Phase Transitions in Nuclei: Spreading the Wings

by Clara E. Alonso, Jose M. Arias, Francisco Pérez-Bernal, and José E. García-Ramos ......................... 33

News and ViewsShell Evolution and Search for Two-Plus Energies at RIBF (SEASTAR): A RIKEN Scientific Program at the Radioactive Isotope Beam Factory

by P. Doornenbal and A. Obertelli .............................................................................................................. 35CUSTIPEN: China-U.S. Theory Institute for Physics with Exotic Nuclei

by Bao-An Li and Furong Xu ....................................................................................................................... 36

ObituaryIn Memoriam: Erich Vogt (1929–2014)

by Jean-Michel Poutissou and Ewart Blackmore ........................................................................................ 38

Calendar.......................................................................................................................................................... 39

editorial


The views expressed here do not represent the views and policies of NuPECC except where explicitly identified.

The field of nuclear medicine covers all medical uses of open ra-dioactive sources emitting ionizing radiation that are introduced into the patient for the purpose of diagnostics or therapy.

Nuclear physics has since its be-ginning been characterized for fast implementation of its discoveries to the benefit of humankind. Its medi-cal applications constitute the fastest science transfer from basic research to social applications. When the ef-fects of ionizing radiation were dis-covered, radioisotopes were rapidly introduced into medical practice for treatments. Röngten discovered the X-rays and demonstrated its medi-cal use when he made a picture of his wife’s hand in a photographic plate. Studies of bone deformations using X-rays were already published the following year. Also, as early as 1913 György de Hevesy studied metabolic processes of plants and animals, by tracing chemicals in the body where he had replaced part of the stable ele-ment with small quantities of the ra-dioactive homolog.

By the creation of the IAEA (Inter-national Atomic Energy Agency) in 1957 a mandate was given to devise methods whereby the fissionable ma-terial would be allocated to serve the peaceful pursuits of humankind. Ex-perts should under the concept of “At-oms for Peace” investigate the possi-ble application of atomic energy to the needs of agriculture, medicine, and to other peaceful activities. The nuclear physics field has fulfilled this commit-ment by far and kept an intimate con-nection between its basic and applied

research. Without the former the prog-ress would have been very reduced in the latter. Applications resulting from basic research contribute to the wealth and health of society. Nuclear medi-cine directly uses numerous achieve-ments in nuclear physics and radio-chemistry, among these more than a dozen of outstanding discoveries and techniques were recognized by Nobel Prizes in Physics and Chemistry.

It is important to stress here that laboratories with focus on basic re-search in nuclear physics and related technology such as accelerator, detec-tor, and isotope-production contribute to the developments in nuclear medi-cine. Further, they also provide con-siderable expertise and advice to cen-ters that are fully dedicated to nuclear medicine. Today they can produce the suitable isotopes used for medical im-aging and treatment. In addition, the techniques used by nuclear physicists to peer “inside” the nucleus can be ap-plied to imaging and to trace agents inside the body. Human functionality and the effects of diseases or drugs can be thus directly studied.

The very strong interface between physics, biology, and medicine and the intense collaborations between their researchers have contributed to the development of novel methods and instruments. Presently medical doctors and physicists are working together and are able to outline global strategies.

In applying nuclear physics in medicine, constructive interaction with physicians is of paramount im-portance. What do physicians ask of nuclear physics? And what is the

medical and physical point of view of hadron-therapy, medical imaging, and radioisotope production? The answers to these questions require some con-sideration and are addressed to some extent in the report that NuPECC is dedicating to “Nuclear Physics for Medicine.” The aim of this book-let is twofold: to communicate to its own community the state-of-the-art of the medical applications of nuclear physics and to show to the society as a whole the value and importance of nuclear research.

The report is divided into three chapters dedicated to hadron therapy, medical imaging, and radioisotope production. In this report we learn that radiation therapy using protons, neu-trons, or heavy ions has become one of the most sophisticated and attractive approaches in the treatment of cancer. In fact, around 100,000 patients have been treated worldwide with protons and a factor of 10 less with heavier ions. A recent French study indicates that that protons and C-ions could be beneficial in approximately 12% and 5% of cancer patients, respectively. These values exceed by far the cur-rent capacities of hadron-therapy programs. Accelerator facilities have evolved in recent decades, going from fundamental research laborato-ries, conceived and built mostly by academic research teams, to turn-key industrial ensembles. One can easily identify spin-off companies from nu-clear physics laboratories such as IBA in Belgium.

Medical imaging originates from nuclear medicine where single pho-ton emission tomography (SPECT)

Nuclear Physics for Medicine

editorial


and positron emission tomography (PET) imaging techniques are used to observe complex biological processes at the early stage of a disease or for therapeutic follow-ups. The SPECT and PET imaging techniques are en-tering a new era, where technical im-provements will play an increasingly important role.

In the third and last chapter of this report one can learn about which ra-dioisotopes are needed for what type of applications, how they are pro-duced today and how radioisotope production keeps profiting from tight synergies with other nuclear physics activities. Radionuclides are the es-sential fuel that drives many nuclear medicine applications, and with a few exceptions they are all produced by accelerators or nuclear reactors.

This report has been elaborated following the successful model used by NuPECC previously where the NuPECC members chose two conve-ners per chapter that steer the work-ing groups chosen for the three topics. NuPECC members and in particular NuPECC liaisons have followed and discussed thoroughly the various steps necessary to prepare the report. The draft reports were published on the NuPECC website and discussed at an open Meeting in Paris on 18 Novem-ber 2013. The input received from the community was incorporated yielding the report published April 2014. This document gives us a detailed pan-orama of the present status of nuclear medicine and showcases our commu-nity in different forums including pol-icymakers and European institutions.

These presentation comments have certainly triggered your curiosity, and thus it is natural to invite you to download the report from http://www.nupecc.org/pub/npmed2014.pdf. Read and enjoy!

Maria José Garcia BorGe

ISOLDE-PH, CERN, Geneva, Switzerland,

and Instituto de Estructura de la Materia, CSIC, Madrid, Spain

Filler, please.

feature article


IntroductionOne of the major challenge in experimental and theoreti-

cal nuclear physics is the understanding of the properties of nuclei with extreme neutron-to-proton ratios. The most ex-treme asymmetric nuclei are located at and beyond the neu-tron drip-line. The first question arising here is the location of the drip-line itself, i.e., where are the limits of nuclear stability. Experimentally, this question is answered today only for the lightest elements up to oxygen [1] with 24O (Z = 8) being the heaviest bound isotope. For fluorine (Z = 9), the drip-line lies considerably further out, with the heaviest bound isotope observed experimentally being 31F [2]. Figure 1 gives an overview on the nuclear chart for the light nuclides for elements up to the fluorine isotopes. Be-sides the stable (black) and bound (red and blue) isotopes, unbound nuclei that have been observed experimentally as resonance states are indicated as well by the green fields. The apparent anomalous behavior of the location of the drip-line for the oxygen isotopes has been recently explained by the impact of three-nucleon (3N) forces, which contribute repul-sively to the interaction among the valence neutrons [3, 4].

Another striking feature observed at the neutron drip-line is the dramatic change in the shell structure. Examples are the vanishing of the N = 8 closed shell in the neutron-rich isotopes 11Li [5] and 12Be [6] and the doubly magic na-ture of 22O and 23O [7–13]. The appearance of the N = 16 closed shell for neutron-rich nuclei has been traced back to the attractive tensor force between protons and neutrons which gradually decreases coming from stable nuclei with N = 16 when protons are removed along the isotones causing the opening up of the N = 16 neutron shell for oxygen [14].

It is thus of central interest how the structure of nuclei proceeds for even more extreme neutron-to-proton ratios (i.e., for neutron-unbound nuclear systems beyond the drip-line). A quantitative theoretical description of the properties of unbound systems meets additional challenges as, for in-stance, the proper inclusion of continuum effects. The exper-imental access of unbound nuclei meets several challenges as well. These are related to low production rates and the difficulty in detecting multi-neutron decays. Also the inter-pretation of measured excitation-energy spectra is often not straight forward due to the fact that neutron-unbound states

Beyond the Neutron Drip-LineThomas aumann1,2 and haik simon21 Institut für Kernphysik, Technische Universität Darmstadt2GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany

Figure 1. Nuclear chart showing the light nuclides of the elements hydrogen to fluorine (Z = 9). The neutron drip-line is firmly established up to the element oxygen (Z = 8), while the heaviest bound fluorine isotope known experimentally is 31F. The green and white boxes mark unbound isotopes (green if identified experimentally applying continuum spectroscopy methods).

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are extremely short-lived (i.e., exhibit large widths resulting in overlapping resonances, which often cannot be resolved). We will discuss a few recent examples in this article high-lighting methods which potentially resolve such ambiguities and thus will enable detailed investigations of continuum states including the determination of their quantum numbers and decay properties. As examples, we discuss angular cor-relations and momentum profiles analyzed for the case of He isotopes, and Li, Be isotopes, respectively. Finally, we will discuss very recent experimental results for the so far heavi-est observed unbound systems beyond the neutron drip-line, which are the oxygen isotopes 25,26O.

Angular Correlations in the Decay of 10HEThe first neutron-unbound ground state of He isotopes

beyond the drip-line, 9He, has been observed experimen-tally in a pion-induced double-charge-exchange reaction on 9Be in Los Alamos [15] (for a summary of experimen-tal results on 9He we refer to the most recent study by Al Kalanee et al. [16]). Going further beyond the drip-line is difficult using such reactions, since for the production of

10He, for instance, a radioactive target would be necessary. The emergence of intense high-energy radioactive beams opened a new way to study nuclei beyond the drip-line [17]. The first experimental evidence for the ground state of 10He came from a measurement at RIKEN by Korshenin-nikov et al. [18] using a one-proton knockout reaction from 11Li. Since then, several experiments have searched for the ground and excited states of 10He yielding partly controver-sial results [19–26].

Different interpretations of the data are often related to the fact that resonances overlap and that the measured en-ergy spectrum appears rather structureless. Angular distri-butions or correlations are a powerful tool to assign quan-tum numbers and to identify different contributions to the spectrum. However, such an analysis is often hampered by too low statistics. A recent experiment [22, 23] performed at the LAND reaction setup at GSI could shed light on this problem by employing a one-proton knockout reaction with a high-energy (280 MeV/nucleon) 11Li beam impinging on a liquid hydrogen target. The 10He energy spectrum was reconstructed from the measured momenta in the three-

Figure 2. Ground and excited states of the unbound 10He. Left: Invariant-mass spectrum reconstructed from the decay of 10He into 8He plus 2 neutrons, produced in a one-proton knockout reaction from 11Li at 280 MeV/nucleon [22, 23]. The curves in the two frames show two different interpretations of the experimental spectrum. Right: Angular and energy correlations observed in the decay of 10He for the decay-energy region 3–7 MeV. The correlations are plotted in 3-body coordinates and compared to calculations under different assumptions corresponding to the two interpretations shown in the double frame to the left. The calculation displayed by the dashed line assumes correlations among the breakup frag-ments identical to those in the initial state 11Li (corresponding to the interpretation of a non-resonant background shown as dotted line in the left figure a). The solid lines correspond to a fit made by using an expansion of the decay amplitude in a restricted series of hyperspherical harmonics assuming Iπ = 2+ and K ≤ 2. The figure is taken from the work of Johans-son et al. [23].

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body decay to 8He plus 2 neutrons (see left frames of Fig-ure 2). The broad peak-like structure cannot be interpreted uniquely and the authors provide two alternative explana-tions. A Breit-Wigner-shaped resonance corresponding to the 10He ground state and a non-resonant correlated back-ground, which could result from initial- state correlations (i.e., from the 11Li ground-state correlations). A phenom-enological wave function for 11Li was used to model this background, which is in accordance with a large amount of experimental observables [27]. Alternatively, the spec-trum might be explained by a superposition of two reso-nances, as shown in frame (b) in the left part of Figure 2. The right panel of Figure 2 show the angular and energy correlations in a three-body coordinate system for the 10He energy region 3–7 MeV. The differences between the two interpretations (solid and dashed curves) are striking, and the excellent agreement between data and the prediction clearly demonstrates that the cross-section in that energy region reflects a 2+ resonance state.

There are still remaining discrepancies in the interpre-tation of different experiments on 10He. All knockout ex-periments [20, 22, 23, 25] are in agreement with each other concerning the energy of the ground-state resonance. These include different reaction mechanisms by utilizing different

targets and/or different types of reactions. The most recent experiment from MSU [25] used a two-proton knockout re-action to populate states in 10He. The result is in very good agreement with the data shown above and the older knockout experiments. Why the transfer experiments from DUBNA [21, 24] result in a significantly higher ground-state energy remains an open question. Also the clarification of excited states beside the 2+ resonance needs further experimental work. Here, we refer to the discussion by Chulkov et al. [26].

Momentum Distributions Observed in the Production of 10LI AND 13BE

A similar state of affairs as discussed above for the un-bound 10He isotope is found for other unbound nuclei (e.g., also for the unbound neutron-rich Be isotopes). In order to shed more light on such discrepancies, the method of momentum-profile analysis has been proposed recently by Aksyutina et al. [28]. This method is based on a measure-ment of the recoil momentum as a function of decay energy after one-neutron knockout. It is well known, that the re-coiling fragment momentum distribution after one-nucleon knockout at high energies reflects the intrinsic momentum distribution of the knocked nucleon. The populated states

Author's personal copy

Yu. Aksyutina et al. / Physics Letters B 718 (2013) 1309–1313 1311

Fig. 2. Upper panel: Momentum profile for the 6He + n system after one-neutronknockout from 8He. The solid line is the calculated p-wave momentum profile,which is fitted to the experimental data. The s- and d-profile functions are alsoshown as an illustration of the large separation between the different l components,which makes this type of analysis very sensitive. Lower panel: Relative energy spec-trum for 6He+n [8]. The solid line is the result of an R-matrix fit to the data foldedwith the experimental resolution [8]. The inset shows the profile function in thelow energy region, where the deviation is interpreted as due to knockout from a(1s1/2)2 component in the 8He ground-state wave-function.

in the E f n spectrum [7] determined from the fit: Pr.e.(E f n) =√αsσ

2s + (1− αs)σ

2p , where σ 2

s and σ 2p are calculated variances

for l = 0 and l = 1, respectively. The profile function Pr.e.(E f n) ishere given up to 6 MeV and one notes that the fit with only sand p components follow the experimental data only up to about1.5 MeV. In the energy region from 1.5 MeV on one notes an in-creasing excess all the way up to the top of the spectrum. Thisexcess is interpreted as due to knock-out from (d5/2)2 compo-nent in the 11Li ground-state wave-function. The relative weight of(d5/2)2 component in the E f n spectrum αd was obtained by usingthe relation: αd = (P2

exp − P2r.e.)/(σ

2d − P2

r.e.) for E f n > 1.5 MeV. Thesize of this contribution is 11(2)%, a result which is in agreementwith the earlier determined value of 17(5)% obtained in Ref. [11]from an analysis of the transverse momentum distribution. Onecan also see that the fit to the relative energy spectrum falls belowthe experimental data at high energies. The knock-out from thed-wave states populates the narrow states in 10Li, with structure[d5/2⊗(3/2−)]1−,2−,3−,4− . We can, however, not resolve such stateswith our experimental resolution but the profile function analysisadds the information that the d-wave strength is distributed in theenergy region between 1.5 to 6 MeV.

While the high-statistics data for 7He and 10Li has been dis-cussed earlier [7,8] we present here, as our third case, for the firsttime the new data for 13Be. Also here the resolution and statisticsare superior to that of our earlier paper [11]. A major problemin the interpretation of 13Be originates in the complex nuclearstructure of the neutron-rich beryllium isotopes. It was enunci-ated already in 1976 that several observed properties of the T = 2,Iπ = 0+ states of A = 12 nuclei favor a model of the 12Be ground-

Fig. 3. Upper panel: Momentum profile of the 9Li + n system after one-neutronknockout from 11Li. The calculated s-(dashed), p-(dotted) and d-wave (dash-dotted)momentum profiles are shown together with a solid line determined from the s-to-p ratio derived from the data in the lower panel. The thin-solid line is a smooth linethrough experimental points. Lower panel: Relative energy spectrum for 9Li+n [7].The different contributions from a R-matrix fit to the data, folded with the ex-perimental resolution, are shown as dotted (virtual s-state) and dashed (p-waveresonance) lines with the solid line as their sum.

state wave-function being made up of only small components thatbelong to the lowest shell-model configurations, while instead s-,p- and d-shells are populated with almost equal weights [12,13],

12Be(g.s.) = α[10Be ⊗ (1s1/2)

2]

+ β[10Be ⊗ (0p1/2)

2] + γ[10Be ⊗ (0d5/2)

2]. (2)

Here, 10Be forms an inert core with a closed 0p3/2 neutron shell.This conjecture has actually been confirmed in a series of recentexperiments [14–18]. In Ref. [14] it was found that N = 8 is nota good closed shell for 12Be since it contains a major (s2 − d2)intruder configuration. This breakdown of the N = 8 shell clo-sure is also expected theoretically [13,19–24]. This means that thestructure of 12Be essentially is of few-body character and that adescription of 13Be with a 12Be core having a closed p1/2 shellis not a good approximation. The open decay channels from 13Beto excited states in 12Be makes the situation even more compli-cated [11,25]. If the remaining fragment, after neutron knockoutfrom a Borromean nucleus, is left in an excited, gamma-decayingstate, the corresponding peak in the E f n spectrum will be shiftedtowards low energies by the excitation energy of the fragment.

The difficulty in the interpretation of 13Be data is illustrated bythe three relatively recently published data sets, all with differentinterpretation of the momentum content around 0.5 MeV in theexcitation spectrum. From data obtained at GANIL [26] it is inter-preted as a Breit–Wigner l = 0 resonance; from the one-neutronknockout data from 14Be, measured earlier at GSI, as a dominatingvirtual s-state [11]; and, finally, from data obtained at RIKEN [25]it is interpreted as an l = 1 resonance together with a small con-tribution from a virtual s state.

1312 Yu. Aksyutina et al. / Physics Letters B 718 (2013) 1309–1313

Fig. 4. Upper panel: Momentum profile of the 12Be + n system after one-neutronknockout from 14Be when impinging on a hydrogen target. The results of model cal-culations are shown as a dashed line (s-wave), a dotted line (p-wave) and a dashed–dotted line (d-wave). Lower panel: Relative energy spectrum for 12Be + n and itsresonance-state decomposition based on the interpretation given in Ref. [11]: (1) –1/2+ , (2 & 4) – 1/2− , (3 & 5) – 5/2+ .

In order to shed more light on this discrepancy and to over-come it, we here apply the profile function analysis to our newdata, and limit in this Letter the discussion to relative energy upto 1 MeV in 12Be + n. Due to the complexity of the 13Be case wegive here only two distinct results in this Letter where the profilefunction gives additional insight. A complete analysis of 13Be, withthese results in mind, will be the subject of a forthcoming paper.

The relative energy spectrum 12Be − n is shown in the lowerpanel of Fig. 4. As a starting point for the present discussion weperform an R-matrix fit to our new data under the same assump-tion of the relative s-, p- and d-contributions as in Fig. 10 ofRef. [11]. With the improved resolution one notes immediatelythat the low energy part of the relative energy spectrum can-not be described with these assumptions alone. This observationcombined with the profile function indicates that the low en-ergy strength must originate in a d-wave contribution. This maybe understood as follows: There is one state in 13Be [27–30] atan energy of about 2 MeV, which is expected to be 5/2+ state.This state would then have one component with the structure[12Be (2+) ⊗ (1s1/2)]5/2+ [31,32], which can decay via neutronemission to the 2+ state in 12Be. The 12Be (2+) state is thende-excited via γ -emission to the ground state of 12Be. Kondo etal. [25], observed indeed neutron-gamma coincidences at low E f n ,and the profile function adds the information that origin of the in-crease of the profile function above the p-wave curve is due toits origin in a 5/2+ resonance in 13Be. In the interval from thebeginning of the relative energy to 0.5 MeV one observes a rapiddecrease of the experimental profile function, far below values ex-pected for a p-wave. The pure fact that the profile function fallsdown close to the s curve is an indication of a large s contri-bution. In the region from 300 keV to 1 MeV assuming only s-and p-contributions, one may estimate in the order of 60% s-wave

contribution. The presence of an additional d configuration in thisregion would result in an even larger value. This is rather in favorof the interpretation given in Refs. [26] and [11]. A 1/2+ state atlow energy in 13Be should have the configuration

13Be(1/2+)

= ζ[10Be⊗ (0p1/2)

2 ⊗ (1s1/2)]

+ η[10Be ⊗ (0d5/2)

2 ⊗ (1s1/2)]. (3)

The maximum at 0.5 MeV in the relative energy spectra fromRefs. [11,25] and from data analyzed here is more narrow thanthe ones in Ref. [26] where states of 13Be have been populated byproton knockout from 14B. The large momentum transfer to thecore in a knockout of a tightly-bound proton can be the reason.Such an effect has been observed in [6] for the 8He + n system inproton knockout reactions from 11Li.

The conclusion, based on the information from the momentumprofile analysis, is that the main peak in the relative energy spec-trum 12Be + n, is to a major part associated with an s state.

In summary we have used an experimental observable, the mo-mentum profile function of the remaining fragment + neutronsystem after one-neutron knockout from a Borromean nucleus,to study details in the angular momentum content in the binaryresidue. This method have the same limitations as those for mo-mentum distributions: high beam energy is needed in order adoptimpulse approximation and a hydrogen target is preferable. Wehave observed the following new results:

(i) The 7He data reveals the presence of an (s1/2)2 componentin the 8He ground-state wave-function.

(ii) The 10Li data reveals an 11(2)% (d5/2)2 component in the11Li ground-state wave-function. The d-wave strength is found tocontribute to the 10Li relative energy spectrum in the energy re-gion above 1.5 MeV.

(iii) We confirm an s wave neutron decay from a 5/2+ statein 13Be to the 2.1 MeV 2+ state in 12Be. It is shown that themaximum in the 13Be relative energy spectrum has a strong con-tribution from an s state.

Acknowledgements

The authors are indebted to A. Bonaccorso and A. Heinz for nu-merous discussions.

This work is partly supported by the Helmholtz InternationalCenter for FAIR within the framework of the LOEWE programlaunched by the State of Hesse. Financial support from the SwedishResearch Council and the Spanish Ministry through the researchgrant FPA2009-07387 is also acknowledged.

References

[1] B. Jonson, Phys. Rep. 389 (2004) 1.[2] P.G. Hansen, Phys. Rev. Lett. 77 (1996) 1016.[3] D. Bazin, et al., Phys. Rev. 57 (1998) 2156.[4] D.E. Greiner, et al., Phys. Rev. Lett. 35 (1975) 152.[5] T. Aumann, et al., Nucl. Phys. A 640 (1998) 24.[6] H.T. Johansson, et al., Nucl. Phys. A 842 (2010) 15.[7] Yu. Aksyutina, et al., Phys. Lett. B 666 (2008) 430.[8] Yu. Aksyutina, et al., Phys. Lett. B 679 (2009) 191.[9] Z.X. Cao, et al., Phys. Lett. B 707 (2012) 46.

[10] K. Hagino, N. Takahashi, H. Sagawa, Phys. Rev. C 77 (2008) 054317.[11] H. Simon, et al., Nucl. Phys. A 791 (2007) 267.[12] F.C. Barker, J. Phys. G: Nucl. Part. Phys. 2 (1976) L45.[13] F.C. Barker, J. Phys. G: Nucl. Part. Phys. 36 (2009) 038001.[14] A. Navin, et al., Phys. Rev. Lett. 85 (2000) 266.[15] S.D. Pain, et al., Eur. Phys. J. A 25 (2005) 349.[16] H. Iwasaki, et al., Phys. Lett. B 481 (2000) 7.[17] S. Shimoura, et al., Phys. Lett. B 654 (2007) 87.[18] R. Kanungo, et al., Phys. Lett. B 682 (2010) 391.

Figure 3. Momentum profile (upper frames) and decay-energy spectrum (lower frames) for the decay of 10Li (left frames) and 13Be (right frames) into fragment plus one neutron after population in a one-neutron knockout reaction from 11Li and 14Be, respectively. The data have been taken at GSI at beam energies of 280 and 304 MeV/nucleon, respectively, using a liquid hydrogen target [28]. The curves in the upper frames show the theoretical expectation for the momentum width (rms) for different angular momenta. The figure is taken from the work of Aksyutina et al. [28].

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in the A-1 fragment depend on the ground-state configura-tion from which the nucleon is knocked out. An example is shown in the left part of Figure 3 for the well known 10Li case. The lower figure shows the decay spectrum exhibiting two structures below 1 MeV corresponding to the low-lying virtual s-state and the p-wave resonance at a bit higher en-ergy. This interpretation is proven right by inspecting the momentum profile as a function of decay energy shown above. For each energy bin, the root-mean-square width of the momentum distribution of the recoiling 10Li nucleus is shown (reconstructed from measured 9Li and neutron mo-menta). The comparison with the theoretical estimates for knockout from s2, p2, or d2 configurations in 11Li shows the l = 0 character of the low-lying peak with an increasing width originating from the l = 1 state at around 0.6 MeV. At higher energies, the momentum width becomes larger due to a contribution from the d-state.

Applying the same method to the 13Be case produced in one-neutron knockout from 14Be reveals additional insight to the origin of the low-energy spectrum of 13Be. It is clearly seen that the low-energy shoulder of the peak at around 0.4 MeV originates from a d-wave contribution, while the main peak has a dominant l = 0 character. In combination with the experiment performed at RIKEN by Kondo et al. [29] it can be concluded that the d-wave component visible at the threshold results from the d5/2 state in 13Be at around 2 MeV, which decays via the bound 2.1 MeV 2+ state in 12Be. Again, this example demonstrates the power of the kinematical complete measurements of the population and decay of unbound states, which provide additional observ-ables to clarify continuum structures even in the case of complex situations with overlapping resonances.

The Unbound Oxygen Isotopes 25,26OThe heaviest unbound nuclei beyond the neutron drip-

line, for which experimental spectroscopic information is available, are the oxygen isotopes 25,26O. An unbound reso-nance state at 770+

–2100 keV was reported first by Hoffman et

al. [11], and confirmed by Caesar et al. [4]. The heaviest isotope 26O was discovered only recently in proton knock-out experiments at MSU [30] and GSI [4]. Both measure-ments agree with the finding that the ground state is located at very small decay energy with an upper limit of 120 keV at 95% c.l. [4]. The result from the MSU measurement is shown in Figure 4.

The ground-state energies measured for 25,26O are compared in Figure 5 to theoretical shell-model predic-tions based on chiral two-nucleon (NN) and 3N forces (NN+3N) by Caesar et al. [4]. The role of 3N forces in the context of the drip-line for the oxygen isotopes has been

discussed previously by Otsuka et al. [3]. The anomalous location of the drip-line for the oxygen isotopes is attribut-able to the repulsive contribution provided by 3N forces to the interaction of valence neutrons. The calculation shown in Figure 5 takes into account for the first time also resid-ual 3N forces, which become increasingly important with the addition of valence neutrons. The effect can be seen in Figure 5 by comparing the solid lines with dashed-dotted lines. While the impact of the residual 3N forces is rather small for 24O (about 0.1 MeV), it increases the ground-

3

10 20

5

10

0

1

2

3

E (

Me

V)

F27

OO+nO+2n262524

(-pn)

(-p)(-p)

FIG. 4: (Color Online) (a) Decay energy spectrum of25O (two-body, fragment + n system). The data are the same as in

Figure 3. The inset indicates the different decay paths. (b,c,d) decay energy spectra of26O (three-body, fragment + n + n

system). The grey area in (b) represents the simulated cross-talk contribution. The individual contributions to the cross-talk

from the different simulated states are shown in the inset. Panel (c) shows the cross-talk subtracted26O spectrum. Panel (d)

shows the26O spectrum with causality cuts applied to the data as well as the simulation. The lines are explained in the text.

order to fit the data, we performed Monte Carlo simula-

tions which included the geometrical acceptances, energy,

positions, and timing resolution, tracking of the charged

particles through the Sweeper magnet, and the reaction

and decay mechanisms. The interaction of the neutrons

with MoNA was described using the Geant4 simulation

package [35] with the addition of the MENATE-R physics

class [36]. Thus, multiple interaction of a single neutron

were fully included in the simulations.

A low-energy resonance was simulated with a Breit-

Wigner line shape and the energy from the 26O decay

into 24O and two neutrons was partitioned between the

three outgoing particles according to the phase-space

model of references [37, 38]. The data are not sensitive

to the detailed parameters of the various possible con-

tributions to the high energy continuum. As shown in

Figure 1, the continuum shell model predicts only one

excited state for 26O at approximately 2 MeV with the

next excited state calculated at about 6 MeV [25]. Thus,

a resonance in 26O at a fixed energy of 2 MeV with a

width of 200 keV, which was allowed to decay sequen-

tially via the known unbound ground state of 25O, was

included in the simulation. The resonance parameters for25O (Edecay = 770 keV, Γdecay = 172 keV, L = 2) were

taken from reference [26]. A χ2 fit to the two-body and

three-body system was performed where the resonance

energy and width of the low-energy resonance and the

relative strengths of the three contributions (low-energy

and 2 MeV state in 26O and the ground state of 25O)

were free parameters.

Figure 4 shows the resulting simulated spectra for the

best fit parameters (solid line). The two-body and three-

body systems are shown on panels (a) and (b), respec-

tively. The low-energy resonance in 26O at Edecay =

150 keV and Γdecay = 5 keV is shown by the long-dashed

red line and the 2 MeV resonance by the short-dashed

green line. The dot-dashed blue line shows the contribu-

tion from the direct population of the 25O ground state.

These decay paths are also indicated in the inset of Fig-

ure 4(a). In the simulation it is possible to distinguish

real two-neutron detection from cross-talk events where

a single neutron interacted twice in MoNA. The grey-

shaded area in Figure 4 (b) shows the contributions of

the simulated cross-talk events to the total spectrum. In

the inset the individual contributions to the cross-talk

from the low- and high-energy 26O decays as well as the

contribution from the 25O are shown. In order to demon-

strate the positive signal of real 2n events we applied

two different methods. First we subtracted the simu-

lated cross-talk events from the data, and the results are

Figure 4. Relative-energy spectrum for the 24O+n+n sys-tem produced in a proton knockout reaction from 27F at 82 MeV/nucleon. The experiment has been performed at the NSCL using the MoNA neutron detector. The rise of the in-tensity at very low relative energies is interpreted to stem from the population of the 26O ground state (long-dashed curve). The figure is taken from Lunderberg et al. [30].

0

0.5

1

1.5

Ener

gy (M

eV)

26O

2+

25O

NN+3NNN+3N + residual 3N

3/2+

0+

24O

0+

MoNA/NSCL (2008, 2012)R3B-LAND (this work)

Figure 5. Comparison of the experimental 25O and 26O en-ergies with theoretical shell-model calculations based on chiral NN and 3N forces (NN+3N) and including residual 3N forces. The figure is from the work of Caesar et al. [4].

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state energy of 26O relative to 24O by 0.4 MeV, bringing the theoretical value very close to the measurements. The remarkable agreement with experiment should, however, be considered with caution since the continuum effect has not been included in that calculation. This effect might be rather small for the 26O ground state with its very narrow low-lying resonance, but will be of importance, however, for predictions of excited states and 28O. The measure-ment of the 28O ground state will certainly be one of the next experimental challenges, which meets besides the low production rate additionally the difficulty of four-neutron detection. At the presently most powerful facil-ity providing high-energy fragmentation beams, RIBF at RIKEN in Japan, such an experiment might be in reach in the not too distant future.

Another interesting aspect related to the very low-lying ground-state resonance in 26O is the possibility of a rather long lifetime as suggested by Grigorenko et al. [31], which would constitute the first case of two-neutron radioactivity. Caesar et al. [4] extracted an upper limit for the lifetime of 5.7 ns at a 95% confidence level from the measurement of the 26O ground state. In an experimental work by the NSCL-MoNA group at MSU [32], a half-life T = 4.5+1.1(stat)1/2−1.5 ± 3(syst) ps T1/2 = 4.5+

–11..15 ± 3 (syst)

ps has been extracted, corresponding to a lifetime of 6.5 ps. At an 82% confidence level, a finite lifetime of the 26O ground state is claimed [32]. Even the combination of both results does not allow for a firm conclusion (5s signal) on the possibility of neutron radioactivity. It would thus be ex-tremely exciting to perform a dedicated and optimized ex-periment with good statistics to measure the lifetime of 26O.

ConclusionTremendous progress in the experimental investigation

of nuclei beyond the neutron drip-line has been achieved in recent years. It turned out that a kinematically complete measurement of the decay of unbound states populated in high-energy knockout reactions is a very powerful tool. The observation of angular, energy, and momentum correlations allows thereby to disentangle different contributions in the continuum spectrum of overlapping resonances and iden-tify unbound states and assign their quantum numbers. Still, many open questions and also contradictory experimental results or interpretations remain that have to be clarified ex-perimentally. A precise measurement of the energy of the

very low-lying 26O ground state and the determination of its life time is only one example. The observation of the 28O ground state would be a major step forward and an impor-tant benchmark for ab-initio theories. Although extremely challenging, such a measurement might be within reach in the not too distant future.

AcknowledgmentsThe authors acknowledge support via HIC for FAIR,

EMMI, BMBF, and GSI.

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feature article


Accelerating expansion of the Universe was discovered in the observations of distant Supernovae 1a, and recog-nized by the 2011 physics Nobel Prize. How to understand this acceleration brings together many aspects of modern physics, including much of interest to nuclear physicists.

Within Einstein’s theory of General Relativity, the ac-celerating expansion of the Universe is interpreted as a small positive cosmological constant or vacuum energy density, called “dark energy,” perceived by gravitational interactions of +(0.002 eV)4. This vacuum energy density extracted from astrophysics is 1044 times smaller than the value expected from mass generation mechanisms associ-ated with the non-perturbative condensates of Quantum Chromodynamics (QCD, the theory of quarks and gluons) and 1056 times smaller than the value expected from the electroweak Higgs sector in particle physics, which also comes with a negative sign. The cosmological constant connects the large scale structure of the Universe with the subatomic vacuum [1–3]. Why is the net vacuum energy density finite, positive, and so very small?

Supernovae 1a act as “Standard Candles” to probe the expansion of the Universe. These events come from the explosion of dense white dwarf stars after accumulating matter from a companion star. Because of the special ther-monuclear dynamics, these explosions all occur with same brightness making them a good measure of large-scale structure, distance, and the expansion of space. Observa-tionally Supernovae 1a are well studied with about 1,000 observed events. Open questions in nuclear astrophysics in-clude possible progenitor stellar systems for the supernova and what triggers the thermonuclear explosion and causes the white dwarf star to explode?

Here we outline the key physics issues and how they touch issues in frontline nuclear physics research.

The subatomic physics vacuum is not empty but filled with condensates associated with spontaneous symmetry breaking. These condensates each give a contribution to the energy of the vacuum. Positive net vacuum energy density

(the energy of “nothing”) corresponds to negative pressure and drives the accelerating expansion of space. (The vac-uum expectation value of the energy-momentum tensor is proportional to the metric, ɡmν, so one finds ρ = –p for the vacuum or cosmological constant equation of state.) When the density of matter (including both visible and possible dark matter) dominates, the expansion decelerates due to normal gravitational attraction. When the Universe expands to the point that matter becomes dilute and the matter den-sity falls below the vacuum energy density, then the expan-sion of the Universe changes from deceleration to accelera-tion. Supernovae 1a observations tell us that this occurred about five billion years ago, corresponding to redshift about one. This age compares with the earliest single cell bacteria on Earth, which date from about 3.5 billion years. Today we find a consistent picture from observations of supernovae, the cosmic microwave background and large scale ripples in the distribution of galaxies. The Universe is spatially flat over large (greater than galactic) scales with energy budget consisting of 68% dark energy, 5% visible matter, and 27% dark matter.

The net vacuum energy is measured only through large distance gravity and astrophysics. This is because gravity couples to everything whereas other physics processes and experiments involve measuring the differences between quantities. Before we couple to gravity, only energy differ-ences have physical meaning, for example, in Casimir pro-cesses which measure the force between parallel conduct-ing plates in QED and which contribute a “cavity term” to the mass of the proton in Bag models of quark confinement.

Mass generation processes in particle physics are, in general, associated with condensates and non-zero vacuum energies. QCD confinement and dynamical chiral symme-try breaking generates the constituent quark mass (about 300 MeV), the mass of nucleons, and 98% of the mass of the visible Universe, which interacts through normal attrac-tive gravitational interaction. Dynamical chiral symmetry breaking in QCD is associated with the pion cloud of the

The Cosmological Constant Puzzle: Synergies with Nuclear Physics and its Measurement in Astrophysics Experiments

Steven D. BaSS

Stefan Meyer Institute for Subatomic Physics, Austrian Academy of Sciences, Vienna, Austria

feature article


nucleon and also with a quark condensate which acts as an order parameter for the QCD phase transition. A gluon con-densate is also expected. These condensates were formed in first 10–5 seconds of the Universe. The QCD phase dia-gram with density and temperature dependence [4] is an important topic for investigation at the future FAIR facility at Darmstadt and in relativistic heavy ion collisions (e.g., at RHIC and the LHC). The QCD condensates associated with mass generation give a vacuum energy density contribution of –(200 MeV)4 from the Mexican hat potential in the vac-uum associated with spontaneous chiral symmetry break-ing. From the Higgs, one finds –(250 GeV)4. What cancels these large QCD (and Higgs) condensate contributions to give the net vacuum energy density (0.002 eV)4 extracted from astrophysics? It is curious that the dark energy scale 0.002 eV is close to the range of possible values expected for the light neutrino mass: Is this a clue? Understanding dynamical symmetry breaking (in particle physics) when we couple to gravity is an open and exciting challenge in modern physics [1, 2].

Supernovae 1a are an ideal tool for mapping out the accelerating expansion of the Universe [5, 6]. These as-trophysical events are caused by runaway thermonuclear explosions of dense carbon or oxygen white dwarf stars following accretion of matter from a nearby companion red giant star or perhaps a second white dwarf. They have al-most uniform brightness making them “Standard Candles” which can be used for the precise measurement of astro-nomical distances. Light from these sources is fainter than expected for a given expansion velocity, indicating that the supernovae are farther away than predicted with just nor-mal matter densities and no dark energy, indicating that the expansion of the Universe has been accelerating during the last five billion years.

The peculiar thermonuclear explosions of Supernovae Type 1a allow them to be used as Standard Candles to study the expansion of space. Supernova1a are well studied in ob-servations. The reason for these explosions is an open prob-lem in nuclear physics. What are the possible progenitor systems (white dwarf plus what types of companion star) and how does the explosion start?

White dwarfs are the remains of stars about the size of the Sun. They are very dense objects, second only to neu-tron stars and black holes and inert, emitting only thermal radiation. A teaspoon of matter from a white dwarf would weigh five tons. Because of its density, the gravity of a white dwarf star is intense. A white dwarf will pull mate-rial off any companion star (e.g., a red giant, accreting that matter to itself or, possibly, merge with a companion white dwarf). When the mass of a white dwarf reaches 1.38 so-

lar masses a nuclear chain reaction occurs causing the star to explode. Increasing pressure and density due to the in-creased mass raises the temperature of the core. Convection and carbon burning takes place lasting about 1,000 years until a large instability is formed that becomes runaway and completely disrupts the star within seconds. A deflagration flame starts, powered by carbon fusion. Where and at how many points the flame begins is unknown. Oxygen fusion then starts but is slower than carbon fusion. A substantial fraction of the carbon and oxygen is burned to heavier ele-ments within just a few seconds releasing vast energy and causing the star to explode. The details of how exactly how the burning front moves through the star and what causes the deflagration to detonation transition are unknown. The observed light from the supernova is powered by the radio-active decay 56Ni → 56Co → 56Fe. The rise to maximum light (brightness) takes about 17–20 days and is followed by rapid decline. Supernovae 1a occur with uniform bright-ness about five billion times the Sun. They occur in a galaxy about three times per millennium.

Besides a cosmological constant, ideas for modeling the observed accelerating expansion of the Universe include the vacuum expectation value of a possible new, very-light mass, time-varying scalar field (which may have been large near the very start of the Universe), possible long distance modifications of general relativity and anthropic argu-ments. These ideas though still come with the challenge of how to explain the “discrepancy” between the astrophysics value and large vacuum energy density expected from par-ticle physics. Any effect which produces time dependence of dark energy might also induce time dependence in other fundamental couplings and masses (e.g., the fine structure constant α or the ratio of electron to proton masses). Here strong constraints exist from measurements in quantum optics (today), from studies of transitions in molecules in space (dating back 10–12 billion years), and from the cos-mic microwave background (light from when the Universe was 138,000 years old). Confirming General Relativity at large distances and mapping the equation of state for the vacuum dark energy is a prime goal for future precision dark energy research (e.g., with the planned Euclid ESA space mission and the ESO European Extremely Large Telepscope in Chile). Is the accelerating expansion of the Universe really driven by a time independent cosmological constant or by new possibly time dependent dynamics?

Understanding the accelerating expansion of the Uni-verse and the cosmological constant vacuum energy puzzle promises to teach us a great deal about the intersection of subatomic physics and dynamical symmetry breaking on the one hand, and gravitation on the other. The nuclear as-

feature article


trophysics of supernovae 1a explosions contains interesting theoretical puzzles to be solved.

References1. S. Weinberg, Rev. Mod. Phys. 61 (1989) 1; J. A. Frieman, M. S.

Turner, and D. Huterer, Ann. Rev. Astron. Astrophys. 46 (2008) 385; J. Lesgourgues, PoS EPS-HEP2011 (2011) 015.

2. S. D. Bass, J. Phys. G 38 (2011) 043201; arXiv:1210.3297 [hep-ph].

3. L. Amendola and S. Tsujukawa, Dark energy: theory and ob-servations (Cambridge University Press, Cambridge, 2010).

4. P. Braun-Munzinger and J. Wambach, Rev. Mod. Phys. 81 (2009) 1031.

5. A. Goobar and B. Leibundgut, Ann. Rev. Nucl. Part. Sci. 61 (2011) 251.

6. W. Hillebrandt, M. Kromer, F. K. Röpke, and A. J. Ruiter., arXiv:1302.6420 [astro-ph.CO].

Steven D. BaSS

Filler, please.

facilities and methods


IntroductionThe world, as we know, is com-

posed of quarks, gluons, and leptons and it is governed by four fundamen-tal interactions. One of them is the strong interaction, described by the theory of Quantum ChromoDynam-ics (QCD), responsible for the con-finement of quarks inside nucleons. The only way to free experimentally quarks from their confined state is to put the nuclear matter under extreme conditions of high temperature and/or energy density with relativistic collisions of heavy ions. This decon-fined medium is called “Quark Gluon Plasma” (QGP) [1].

ALICE (A Large Ion Collider Ex-periment) [2] is one of the four experi-ments at the Large Hadron Collider (LHC) at CERN in Geneva. The main objective of ALICE is the study of nucleus-nucleus collisions at a center-of-mass energy (for lead nuclei, Pb208) of 5.5 TeV per nucleon.

The ALICE experiment is carry-ing out an experimental heavy-ion program started about twenty-five years ago at the Brookhaven Alter-nating Gradient Synchrotron (AGS) and at the CERN Super Proton Syn-chrotron (SPS) at √sNN ≤ 20 GeV and continued at the Brookhaven Relativ-istic Heavy Ion Collider (RHIC) at √sNN ≤ 200 GeV.

Relativistic heavy-ion collisions provide a unique opportunity to study how the properties of a complex sys-tem emerge from the fundamental in-teractions of QCD.

The successful experimental re-sults achieved so far, in parallel with the theoretical developments, indicate that a hot and dense medium, called sQGP (strongly interacting QGP),

is created in heavy-ion collisions at RHIC and LHC.

One tool to measure the proper-ties of the hot nuclear matter created in heavy-ion collisions is to study the passage of particles through it, in a similar way as the properties of atomic matter are described by the ionization energy loss of charged particles with the Bethe-Bloch formula for the av-erage rate of energy loss, dE/dx. The lifetime of the QGP is far too short [3] to measure its properties with external probes. As an alternative, physicists started to utilize the particles gener-ated in the collision to probe the me-dium. Particularly powerful tools are the “hard probes,” which are produced via high momentum transfer processes in the initial hard scatterings and are therefore exposed to the full evolution of the hot QCD matter. The production rates for these probes are calculable in the standard model and can be com-pared in proton-proton (pp), proton-nucleus (p-A), and nucleus-nucleus (A-A) collisions to disentangle the ef-fects of the cold nuclear matter from those due to the hot QCD medium. At the LHC, more than in the RHIC en-ergy regime, high momentum transfer processes are abundant, opening the way to a class of hard probes that be-have as calibrated projectiles to inves-tigate the hot nuclear medium.

Typical hard probes are high-pT partons, which fragment into jets, heavy quarks (charm and beauty), which can be observed as open heavy flavor hadrons, quarkonia (J/ψ, ϒ), and electroweak probes (i.e., γ, Z). While there have been significant pro-gresses in both theory and experiments to characterize the medium-induced parton energy loss (the so-called “jet

quenching” phenomenon) and parton fragmentation, a conclusive picture of such mechanisms is not available yet.

Another way to study the global properties of the Quark Gluon Plasma is via the collective behavior of the bulk of its particles, the so-called “soft probes.” Once the fireball is formed after the collision, its partons start to move chaotically in the QGP. If the medium is strongly interacting, collec-tive behaviors can arise on top of this Brownian motion. Such “flows” of par-ticles are generated by the presence of pressure gradients in the medium and can provide information on the degree of thermalization of the particles in the medium, on its transport properties, and on the size of the fireball.

ALICE is a general-purpose exper-iment designed to investigate a large array of observables that are relevant for the characterization of the medium. In particular, ALICE is equipped with detectors that provide high precision tracking in a wide transverse momen-tum range (from 0.1 GeV/c to 100 GeV/c), excellent particle identifica-tion capabilities and it is designed to operate in the high-multiplicity envi-ronment typical of heavy-ion colli-sions at the LHC. The results achieved so far with the heavy-ion program require a clear understanding of the reference systems given by pp and p-Pb collisions. The former provides a necessary test of the theoretical pre-dictions from perturbative QCD. The latter provides the control experiment needed to disentangle the effects of the hot and dense medium created in Pb-Pb collisions from the “cold” mat-ter that is created p-Pb collisions.

In this article we review few of the most recent key results obtained

Recent Results from the ALICE Collaboration



by ALICE with p-Pb collisions at √sNN = 5.02 TeV and Pb-Pb collisions at √sNN = 2.76 TeV.

Physics ResultsThe main focus of ALICE is the in-

vestigation of the QGP created in Pb-Pb collisions at the LHC. The matter created at the LHC has been measured to have a longer lifetime, larger size, and energy density compared to RHIC [3]. One of the crucial measurements to characterize the fireball created in these collisions is the measurement of the “elliptic flow.” The elliptic flow is given by the second coefficient v2 in the Fourier expansion of the azimuthal particle distribution on the transverse plane with respect to the symmetry plane of the semi-central Pb-Pb colli-sion. A non-zero v2 would indicate a non-isotropic emission of the particles on the azimuthal plane.

The standard description of the flow is based on hydrodynamics, which relies on the assumption that the system is thermalized and there-fore it is possible to define a tem-perature and its thermodynamical variables (entropy, speed of sound in the medium, etc.). The measurements of anisotropic particle emissions can provide information on the thermo-dynamical properties of the matter created in heavy-ion collisions. The initial asymmetries in the spatial ge-ometry typical of a non-central Pb-Pb collision, together with multiple interactions between the constituents of the created matter, give origin to an anisotropy of the particle produc-tion on the transverse plane, which is a clear experimental signature of col-lective flow.

After the first measurements of the elliptic flow for charged particles in ALICE [4], the analysis progressed to the identified particles and over a larger range of transverse momen-tum. The transverse momentum, de-

fined by the component of momen-tum perpendicular to the beam-line, is widely used in collider physics as it carries information on processes that happened at the collision vertex, in particular on the soft and hard pro-duction regimes.

The v2 as a function of transverse momentum, pT, in semi-central Pb-Pb collisions at √sNN = 2.76 TeV (the cho-sen collision centrality corresponds to the 20–40% of the total Pb-Pb cross-section) is reported in Figure 1 for identified particles: pions, kaons, anti-protons, and the multi-strange baryons Ξ and Ω. Figure 1 shows a significant v2 that is steadily increasing up to 3–4 GeV/c. A mass splitting is observed in ALICE (at a given pT, lighter particles carry more flow as they have a larger velocity than heavier particles), which is larger compared to the measure-ments at RHIC.

The observed mass ordering for all the particle species is well reproduced by viscous hydrodynamic model cal-culations at low pT (also shown as

solid curves in the figure). At high transverse momentum the hydrody-namic predictions start to deviate from the data because other effects like the path-length dependence of the energy loss may intervene.

Theoretical models of energy loss predict a hierarchical dependence on the color charge and mass of the pro-jectile parton: ΔEgluon > ΔElight-quark > ΔEcharm > ΔEbottom. The first inequal-ity expresses a larger energy loss for partons with larger color charge (glu-ons). The second and the third arise from the so-called “dead-cone effect” [6], which predicts a suppression of gluon radiation at small angles for partons with larger mass. This effect is expected to vanish when the mass of the quark becomes negligible com-pared to its energy.

It is therefore interesting to com-pare medium effects (i.e., the path-length, color-charge, and mass depen-dence of the energy loss, as well as the collective motion) on heavy quarks versus light quarks and gluons.

Figure 1. Identified particle v2(pT ) measured by ALICE for 20–40% centrality class and compared to viscous hydrodynamic model calculations [5].



The well-established observable to quantify jet quenching on light and heavy quarks is the nuclear modifica-tion factor RAA, defined as the particle yield in Pb-Pb collisions divided by the same yield in pp collisions scaled by the number of binary nucleon-nu-cleon collisions expected in a given Pb-Pb centrality range. The RAA is of-ten measured as a function of the par-ticle pT and collision centrality.

The RAA of prompt D mesons was measured with ALICE in the 0–7.5% centrality class (corresponding to the 7.5% most central Pb-Pb collisions, measured as a fraction of the total Pb-Pb cross-section) in a wider transverse momentum range (2 < pT < 36 GeV/c) compared to the first measurements [7].

As shown in Figure 2, the RAA values for D0, D+, and D*+ agree within the uncertainties and indicate a strong suppression (factor of 4–5 for 5 < pT < 16 GeV/c) of the D-meson yields in Pb-Pb collisions relative to pp collisions. The first measurement of the Ds

+ meson in Pb-Pb collisions is also reported. A suppression of the

Ds+ is observed for 8 < pT < 12 GeV/c,

in agreement within the uncertainties with the RAA of non-strange charmed

mesons in this pT range. The Ds+-

meson yield could be less suppressed at lower pT because of the predicted c-quark recombination with the en-hanced strange quarks in the medium [9], but more statistics is needed to draw a firm conclusion.

The RAA of J/ψ coming from de-cays of B mesons was measured with CMS in the transverse momentum range 6.5 < pT < 30 GeV/c and with ra-pidity |y| < 1.2, as shown in Figure 3 as a function of the collision centrality in the Pb-Pb collisions [10]. The results are reported together with the RAA of prompt D mesons measured with ALICE in the transverse momentum range 8 < pT < 16 GeV/c and rapidity range |y| < 0.5. The selected pT ranges of D mesons and non-prompt J/ψ cor-respond to similar kinematical ranges for the parent b and c quarks, yet the measurements are performed in dif-ferent rapidity intervals. An indication of a difference in the suppression of

Figure 2. RAA as a function of pT for prompt D0, D+ and D*+ and Ds+ for the

0–7.5% most central Pb-Pb collisions at √sNN = 2.76 TeV [8].

Figure 3. RAA as a function of the collisions centrality (defined as the number of participant nucleons weighted by the number of binary nucleon–nucleon col-lisions) for prompt D mesons (average of D0, D+, and D*+) in the transverse momentum range 8 < pT < 16 GeV/c, compared to non-prompt J/ψ measured with CMS with 6.5 < pT < 30 GeV/c [11]. Results from theoretical calculations are superimposed.



charm and beauty can be observed in the most central collisions, consistent with the mass hierarchy expected from various energy-loss models [12–14], like those reported in the figure.

Still on the heavy flavors, a key observable to study the QGP is given by the bound states of heavy quarks (i.e., quarkonia). The suppression of the charmonium production was for a long time considered as one of the main signatures for a deconfined me-dium.

It was predicted [15] that at large enough temperatures, like those of the QGP, bound states of charm and anti-charm quarks (i.e., charmonia), would dissolve due to the screening effects induced by the high density of color charges in the medium. The relative production probabilities of charmo-nium states with different binding en-ergies may therefore provide informa-tion on the properties of the medium, in particular on its temperature.

Given the hotter and denser me-dium created at the LHC, one would expect a stronger effect on the char-

monium production compared to what was measured at lower energies.

It was interesting to observe that the first ALICE measurements of J/ψ suppression in central Pb-Pb colli-sions at √sNN = 2.76 TeV at forward rapidity showed less suppression com-pared to the results from PHENIX in central Au-Au collisions at √sNN = 200 GeV [16].

Recent measurements on the trans-verse momentum and rapidity depen-dence of the J/ψ RAA can add more constraints on the theoretical models towards the interpretation of these re-sults. Figure 4 shows the J/ψ RAA as a function of pT measured by ALICE at forward rapidity for the 0–20% most central Pb-Pb collisions [17], compared to the measurements from PHENIX in 0–20% most central Au-Au collisions. A striking difference is observed, in particular at low pT, where the yield of J/ψ from PHENIX is suppressed by more than a factor of 4 compared to the ALICE measure-ments. This observation can be under-stood if one allows recombination of charm and anti-charm from the bulk

medium in the low-pT region (i.e., Refs. [18, 19]). This is expected to be a more significant effect at the LHC where the production cross-section of hard probes like charm quarks is sig-nificantly larger than at the lower col-lision energies available at RHIC.

The above results are just a sample of the many striking results related to the formation of hot and dense ha-dronic state of matter emerging from the collisions of Pb nuclei.

However, given the complexity of the Pb-Pb colliding system, an im-portant step in the quest for QGP lies in decoupling the effects of “cold” nuclear matter that arise at the initial stage of the collisions, as opposed to the “hot” nuclear matter that charac-terizes the formation of the QGP.

The proton–nucleus system was predicted to be the perfect benchmark for studying these effects because the hot medium effects are expected to be either small or even totally absent. Proton–nucleus collisions can there-fore provide the data needed to under-stand better the properties of Pb-Pb collisions at the energy of the LHC.

Recent results from the analysis of the ALICE p-Pb data at √sNN = 5.02 TeV regard the nuclear modification factor RpPb, shown in Figures 5 and 6 for reconstructed charged jets and for J/ψ at forward rapidity.

The RpPb of charged jets (Figure 5) is compatible with unity over a large transverse momentum range, thus confirming that the suppression of high-energy jets in Pb-Pb collisions is not a result of cold nuclear matter effects.

The results in Figure 6 indicate that at forward rapidity, correspond-ing to the proton direction through the Pb nucleus, a suppression of the J/ψ yield with respect to pp collisions is observed, while in the backward re-gion no suppression is present. Theo-retical calculations, based on nuclear

Figure 4. Transverse momentum dependence of the J/ψ RAA measured by AL-ICE in the 0–20% most central Pb-Pb collisions at √sNN = 2.76 TeV, compared to the results from PHENIX in the 0–20% most central Au-Au collisions at √sNN = 200 GeV [17].



shadowing and energy loss, are in fair agreement with the experimental results (see Ref. [21] and references therein). These results suggest that no significant final-state absorption effect on the charmonium production is re-quired to explain the data.

Interesting results in the p-Pb col-liding system also come from two-particle correlations, which have proved to be an interesting tool to measure the mechanisms of particle production in hadrons and nuclei. These analyses are based on corre-lations in the azimuthal angle φ and pseudorapity η between a particle (also called “trigger”) and an as-sociated particle in given ranges of transverse momentum. In ALICE, both particles are reconstructed in the detectors of the central barrel (i.e., at mid-rapidity). The correlations are determined by counting the number of associated particles as a function of their difference in azimuth (Δφ) and pseudorapidity (Δη). Typically, a two-particle correlation measure-ment shows a jet-like structure com-ing from an initial hard scattering, peaked on the “near-side” at Δφ ~ 0 and Δη ~ 0.

Experimentally, the near-side jet peak shows only a weak evolution

with the event multiplicity. So by sub-tracting the correlations from different event multiplicities from one another, it is possible to remove the jet-like contribution of the correlation.

A recent result from ALICE on two-particle correlations in p-Pb colli-sions at √sNN = 5.02 TeV [22] reveals two long-range elongated “ridge-like”

structures along the Δη axis, one on the near side (Δφ ~ 0) and one on the away side (Δφ ~ π), see Figure 7 when such a procedure is followed.

The ridge on the near side is ac-companied by a second ridge of simi-lar magnitude on the away side, which is observed for the first time in p-Pb collisions.

Such double-ridge structures were found in Pb-Pb collisions at the LHC and are believed to have their origins in collective hydrodynamic phenom-ena occurring in the early stages of the QGP that is created [24]. However, these phenomena are not generally thought to occur in p-Pb collisions, where the size of the collision region is expected to be too small to allow the development of significant collec-tive effects. A similar ridge structure on the near side was also measured in high-multiplicity pp events at the LHC [25].

Figure 8 shows the projection of the left panel of Figure 7 onto Δφ,

Figure 5. RpPb as a function of pT for charged jets reconstructed with anti-kT in p-Pb collisions at √sNN = 5.02 TeV [20].

Figure 6. RpPb as a function of rapidity for inclusive J/ψ with 0 < pT < 15 GeV/c in p-Pb collisions at √sNN = 5.02 TeV [21]. Results are compared to model cal-culations based on shadowing and energy loss.



along with fits that include cosine terms, cos(2Δφ) and cos(3Δφ), which allow the yield and width of the near-side and away-side ridges to be quan-tified above a constant baseline.

This intriguing and unexpected re-sult still needs to be explained theo-retically. Possible explanations of the phenomenon include initial-state ef-fects (gluon saturation [26]) and/or fi-nal-state effects that assume collective patterns, like hydrodynamics, to occur also in p–Pb collisions [27]. Whatever the origin may be, this observation has opened the window on a novel phe-nomenon occurring in p-Pb collisions at the LHC energies. Further analysis of the high-statistics p–Pb data prom-ises to yield exciting results.

ConclusionsThe ALICE detector has collected a

large amount of data so far in different collision systems (integrated luminos-ities of about 5 nb–1 for minimum bias pp collisions in 2010 at √s = 7 TeV, 1.1 nb–1 for pp collisions in 2011 at

√s = 2.76 TeV, 2.12 μb–1 for mini-mum bias Pb-Pb collisions in 2010 at √sNN = 2.76 TeV, 28 μb–1 with central Pb-Pb trigger in 2011 at √sNN = 2.76

TeV and 48.6 μb–1 for p-Pb collisions in 2013 at √sNN = 5.02 TeV), which yielded to a large array of key mea-surements, including those selected in this article.

In particular, the results from Pb-Pb collisions indicate a high degree of collectivity in the particle emis-sion at low-intermediate transverse momentum in non-central collisions, suggesting that the QGP behaves like a viscous fluid.

The heavy-flavor measurements in Pb-Pb collisions reported in this article showed that the hot and very dense medium causes massive energy loss even to heavy quarks produced in initial hard scatterings, as well as melting of quarkonia, which can then be statistically recombined at the LHC energies. The benchmark p-Pb data has yielded a wealth of unexpected results that opened new studies in this collision system. The comparison with theoretical models in both Pb-Pb and p-Pb collisions is therefore a crucial

Figure 7. Δφ and Δη distributions of two-particle correlations measured in p-Pb collisions in the transverse momentum range 2 < pT,trig < 4 GeV/c for the trig-ger particles and 1 < pT,assoc < 2 GeV/c for the associated particles [17]. The z-axis represents the yield of the associated particles normalized to the number of trigger particles.

Figure 8. Projection of Figure 7 onto Δφ. Superimposed are fits containing a cos(2Δφ) shape and a combination of cos(2Δφ) and cos(3Δφ). Also shown for comparison the results obtained with the HIJING generator, used to simulate p-Pb collisions, see [23].



aspect toward a quantitative charac-terization of the QGP.

At the end of the current first long shutdown of the LHC, the operation is expected to restart in 2015 with the goal to continue the heavy-ion pro-gram, consisting in collecting at least 1 nb–1 of Pb-Pb collisions at the top LHC energy, √sNN = 5.5 TeV.

With the more statistics available after the long shutdown and the usage of different triggers we will able to improve the measurements obtained so far.

An upgrade of the LHC machine is foreseen during the second long shutdown, expected in 2019, which will allow a significant increase of luminosity, that is, up to 10 nb–1 of Pb-Pb collisions at √sNN = 5.5 TeV, corresponding to a net factor of 100 compared to the first LHC Run. In parallel to the LHC upgrade, the ex-periments are planning to upgrade their detectors. As part of this strat-egy, ALICE plans to have a new in-ner tracker which will allow novel and precise measurements of rare probes over a broad range of trans-verse momenta. Crucial will also be the upgrades of the read-out and data-processing systems to cope with the expected higher rate.

ALICE is entering a new high-luminosity and high-precision era,

which will open uncharted territories for a much broader and deeper study of the QGP.

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ElEna Bruna

On behalf of the ALICE Collaboration,

Istituto Nazionale di Fisica Nucleare–INFN, Torino, Italy

Filler?



IntroductionThe mass of a nucleus is one of

its most fundamental ground-state properties and reveals the strength of nuclear binding. Investigating the binding energy of nuclei with respect to the number of protons and neutrons in a nucleus is important for advanc-ing nuclear theory and increases our understanding of nucleosynthesis in supernovae and neutron stars. Preci-sion mass measurements on radioac-tive nuclides belong to the state-of-the-art techniques [1, 2]. Presently, four complementary techniques are applied: isochronous and Schottky mass spectrometry in storage rings (IMS and SMS, respectively), mag-netic-rigidity time-of-flight (TOF-Bρ) measurements, and Penning-trap mass spectrometry (PTMS). With measure-ment cycles in the sub-ms range, IMS and TOF-Bρ MS are well suited for very short-lived species while offer-ing moderate relative precision on the level of 10–6. A higher precision is achieved by SMS but with the need for measurement times on the order of several seconds. As soon as masses with a relative precision well below 10–7 are required, PTMS becomes the method of choice.

While reaching for more and more exotic nuclides, these measurements are often hampered by a minute pro-duction rate and a short half-life of the species of interest as well as a high background of contaminating ions [3]. With the ISOLTRAP setup located at the ISOLDE facility at CERN, we suc-ceeded to perform for the first time on-line mass purification and mass mea-surements on radioactive ion beams with a newly developed multi-reflec-

tion time-of-flight mass separator and spectrometer [4]. Time-of-flight (TOF) mass spectrometry is one of the most commonly used analytical tools in all fields of science. It is based on the identification of beam components with respect to their mass-over-charge ratio by separation in flight time to an ion detector. In multi-reflection time-of-flight (MR-TOF) mass ana-lyzers, the ions use a dedicated flight path multiple times while at the same time keeping the size of the device compact. This technique increases the mass resolving power tremendously compared to TOF mass analyzers while keeping the measurement time as short as a few milliseconds. It can thus provide fast separation of ion beams as demonstrated off- and on-line [4–6], mass purification [4] as well as high-precision mass measure-ments [7, 8].

MR-TOF MS SystemsAt present, three MR-TOF devices

are installed at radioactive ion-beam facilities: GSI Darmstadt (Germany) [5], RIKEN (Japan) [6], and ISOLDE/CERN (Switzerland) [9]. An overview of the different design concepts can be found in Ref. [5]. Common to all de-vices is the coupling to an ion source (off- or on-line) as well as a subse-quent radio-frequency ion trap for the preparation of the incoming ion beam. An ion detector can then be placed behind the device to acquire a time-of-flight spectrum or the unwanted species are removed from the beam by use of a fast deflector while the species of interest is provided for further us-age such as PTMS. Both possibilities are realized at the ISOLTRAP mass

spectrometer for short-lived nuclides at ISOLDE/CERN (Figure 1).

In an MR-TOF device, the ra-dioactive ion-beam components are separated in time of flight by mul-tiple reflections between electrostatic mirrors. Due to the mass-over-charge dependent flight times t ∝ √—m/q a spectrum is obtained which can be converted into a mass spectrum using well-known calibrant ions. As an ex-ample, a time-of-flight spectrum of the MR-TOF mass analyzer is shown on the left of Figure 1 where 39K+, 53Cr+, and 53Ca+ appear as distinct peaks. The capability of this method for mass separation but also mass spectrometry lies in the non-scanning operation as well as the possibility to obtain mass spectra on timescales of several mil-liseconds.

In the case of PTMS, the MR-TOF mass analyzer is used for fast mass separation. Penning-trap mass spec-trometry exploits the fact that the mass-to-charge ratio of the trapped particle can be extracted from its cy-clotron frequency vc = q ⋅ B / (2p ⋅ m), where q (m) is the charge (mass) of the ion of interest and B the magnetic field. A commonly used technique to determine the cyclotron frequency in a Penning trap is the so called time-of-flight ion-cyclotron-resonance (TOF-ICR) detection method. In preparation of performing such a measurement, different ion traps are used at ISOL-TRAP (Figure 1): The radioactive ion beam from ISOLDE first passes through a linear Paul trap (RFQ cooler and buncher), in which the ions are accumulated, cooled and bunched. Subsequently, they pass the MR-TOF mass analyzer as well as a “prepara-

Multi-Reflection Time-of-Flight Mass Separation and Spectrometry



tion Penning trap” for beam purifica-tion from unwanted ions that usually compose more than 99% of the ion beam. Finally, the TOF-ICR measure-ment takes place in the “precision Penning trap,” as shown for 82Zn+ in Figure 1 (right).

The possibilities for precision mass spectrometry of exotic nuclides are limited with respect to half-life

and production rate of the ion of in-terest compared to other beam com-ponents, so-called contaminants. As a consequence, this limits the observa-tion time tobs of a single measurement and the total number of ions N detect-able during an on-line experiment. To distinguish between the tiny dif-ferences in mass of isobaric species, the spectrometer has to provide a suf-

ficient mass resolving power, which in the case of the TOF-ICR method is given by

R Dm

�mD

�c

��c

Š c � �c � TRF;

R Dt

2�t�

nT

2

q

�t2

0C .n�T /2

where TRF is the rf-excitation time and c is an experiment-specific di-mensionless constant close to unity. The mass resolving power increases

Figure 1. Schematic overview of the ISOLTRAP Penning-trap mass spectrometer with an illustration of the ion motion and the resulting detector signals for the MR-TOF mass spectrometer (left) and the TOF-ICR technique (right). For details see text.

Figure 2. (a) Mass resolving power as a function of the observation time for ISOLTRAP’s precision Penning trap using TOF-ICR and the MR-TOF system for a typical ion of A/z ≈ 90 [9]. (b) Observation time required for a mass resolving power of R = 100,000 for the systems as above as a function of mass-to-charge ratio.

(a) (b)

MR-ToF MSisobar purification and

mass measurement

RFQ cooler and buncherion accumulation and cooling

ISOLDEion beam

preparation Penning trapisobar separation,

ion cooling and preparation

precision Penning trapmass measurement

Counts

Timeqofqflightq(μs)3,715 4,331

101

103

104

102

100

4,3300 5 10 15 20 25 30

250

275

300

325

350

375

400

425

450

475

timeqofqflightq/µs

excitationqfrequencyq-q1107779q/Hz

B

82Zn

53Cr39K53Ca



linearly with excitation time (and therefore observation time tobs) and can reach millions, as depicted by the black dashed line in Figure 2a) for the ISOLTRAP Penning trap (B = 5.9T) [9]. While this method is well-suited for longer-lived species, one draw-back of this method is the comparable low mass resolving power in the case of short observation times, that is, for nuclides with half-lives well below t1/2 < 100 ms in combination with high background contamination. Nu-merous aims to improve the resolv-ing power of PTMS like the usage of highly charged ions, the octupolar ion-motion excitation or the phase-imaging time-of-flight technique with resolving powers beyond 108 are presently under study but applied to a few specific cases only. An overview of recent developments can be found in Ref. [10].

In an MR-TOF device, the mass re-solving power

R Dm

�mD

�c

��c

Š c � �c � TRF;

R Dt

2�t�

nT

2

q

�t2

0C .n�T /2

is determined by the width in time Dt of a single species signal after a given flight time . The flight time is approxi-mately nT, where n denotes the num-ber of revolutions and T the revolution time. The time width at the detector in the so-called time-focus-plane is de-termined approximately by the initial bunch width from the ion source Dt0 and the broadening of the signal per revolution, DT. Figure 2a shows the mass resolving power as a function of the measurement time for the ISOL-TRAP multi-reflection time-of-flight mass spectrometer and the precision Penning trap for an ion with A/z ≈ 90 (vc ≈ 1 MHz, A is the mass number, z is the charge state). For very short measurement times the mass resolv-ing power offered by MR-TOF MS is up to an order of magnitude higher

than for the conventional TOF-ICR method. Especially, in the super-heavy element research for very high m/q ra-tios, high mass resolving powers can be reached on much shorter timescales with MR-TOF MS [6]. This is exem-plified in Figure 2b where the required observation time for R = 100,000 as a function of mass-to-charge ra-tio is compared for the two different techniques.

The MR-TOF Device as Mass Separator and Purifier

In combination with a fast ion se-lector, the MR-TOF system can be used as a high-resolution mass separa-tor to supply subsequent experiments with isobarically pure ion beams [11]. At the ISOLTRAP setup, this was first demonstrated for short-lived species with the mass purification of 82Zn, which resulted in the first successful Penning-trap mass determination of this nuclide. With a half-life of t1/2 = 228 ms and a yield of about 300 82Zn-ions per second, contaminated with about 6,000 longer-lived 82Rb ions per second, a fast and efficient suppression of the unwanted ions was essential. With the MR-TOF system, a sufficient time-of-flight separation could be achieved in only 2.5 ms, which is about an order of magnitude faster than with the so far state-of-the-art separation technique of mass-selective resonant buffer-gas cooling in a Penning trap. With a Bradbury-Nielsen gate used to deflect the un-wanted ions from the beam axis, a suppression of about 4 orders of mag-nitude in contamination yield can be achieved [4]. The mass of 82Zn is of particular interest for nuclear astro-physics. Masses of exotic nuclei close to magic numbers can shed light on the elemental composition of the outer crust of these stars. The mass of 82Zn was determined with such accuracy to probe the composition of the neutron-

star crust to new depths. With its re-vised binding energy, the presence of 82Zn could be excluded from the crust.

The MR-TOF Device as Mass Spectrometer

Using an MR-TOF device for a mass measurement exploits the fact that the time of flight of an ion is re-lated to its mass-over-charge ratio through t = a √—m/q + b. Measuring the TOF of two well-known refer-ence ions determines the experimental parameters α and β. The first online application for rare isotope beams has been achieved through the mass measurements of 53,54Ca+ [7]. In this case, 39K+ and 53,54Cr+ with well-known mass values were used as ref-erences from which the mass of the unknown nuclides could be deduced with an overall relative uncertainty of 9 ∙ 10–7. The mass measurement of these isotopes nicely demonstrates un-der which circumstances MR-TOF MS is the preferred detection method. In this example, PTMS was utilized up to 52Ca+, at which point half-life as well as production yield in combination with the contamination ratio prohib-ited further Penning-trap mass mea-surements. At neutron number N = 32, spectroscopic evidence claimed the emergence of a new magic number in the calcium isotopic chain, how-ever, knowledge from ground-state properties was missing. With the new masses of 53,54Ca the magic number at N = 32 not only could be unambigu-ously established but the predictive power of modern nuclear theory in-volving three-body forces could be demonstrated [7].

Ito and colleagues recently re-ported the mass measurement of 8Li+ using only one species (12C+) as ref-erence. Instead of determining both, α and β, the parameter β was experi-mentally determined beforehand and assumed constant over the whole mea-



surement. A mass-resolving power of R ≈ 167,000 was achieved within 8 ms yielding a relative mass uncertainty of 6.6 ∙ 10–7 [8]. This can be compared to PTMS on light species as in the case of 11Li+, where an excitation time of 18 ms was needed to obtain R = 86,000, see Ref. [8] for a detailed discussion.

OutlookMR-TOF devices are versatile tools

that have found their way into radioac-tive isotope research. As a tool for fast beam purification they can support existing mass-measurement setups. They can likewise be employed as diagnostic tool for ion-beam analysis as experiments on radioactive beams usually require exact knowledge of the beam constituents. An MR-TOF spectrum can be used to analyze the qualitative as well as quantitative composition of an unknown ion beam as a function of the different produc-tion and ionization parameters [12].

Multi-reflection time-of-flight mass spectrometry is an emerging field that serves needs complementary to exist-ing techniques. The specific appeal of MR-TOF MS lies in the fact that mass measurement with relative uncertain-ties below 10–6 become possible for nuclides with minute production rates,

strong contamination, and half-lives below 100 ms. MR-TOF MS thus en-hances the realm of exotic nuclides accessible through mass measure-ments on low-energy ion beams with application to intriguing questions of nuclear physics such as the structural evolution of exotic nuclides far from stability or the study of super-heavy elements. The implementation of an MR-TOF device is meanwhile fore-seen at a multitude of present and fu-ture radioactive ion-beam facilities, as for example FAIR (Germany), JYFL (Finland), or TRIUMF (Canada).

AcknowledgementsThis work is partly supported by

the Max-Planck Society, the BMBF, the EU through ENSAR and the ISOLDE Collaboration. Susanne Kreim acknowledges support from the Robert-Bosch Foundation.

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27 (2008) 428. 2. A. Kankainen et al., J. Phys. G 39

(2012) 093101. 3. Y. Blumenfeld et al., Phys. Scr. T152

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7. F. Wienholtz et al., Nature 498 (2013) 346.

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12. S. Kreim et al., Nucl. Instrum. Meth. B 317 (2013) 492.

SuSanne Kreim

CERN, Geneva, Switzerland, and Max-Planck-Institut für Kernphysik,

Heidelberg, Germany

F. Wienholtz

Ernst-Moritz-Arndt Universität, Greifswald, Germany

r. n. WolF

Max-Planck-Institut für Kernphysik, Heidelberg, Germany,

and Ernst-Moritz-Arndt Universität, Greifswald, Germany

Filler?


impact and applications

Nuclear fission energy has incom-parable huge advantages than other energy in solving the conflicts be-tween rapid growth of energy needs and environmental protection be-cause of its high energy density, low-carbon emissions and the potential for sustainable development. Especially in China, the energy structure is in a critical period of strategy transition from coal-based high-carbon energy to low-carbon energy. Development of nuclear energy has become one of the strategic focuses of China’s me-dium and long-term energy develop-ment plan.

Th-U Fuel CycleFissionable nuclear fuel can be di-

vided into two categories, Uranium-based and Thorium-based. Currently, fuels of the entire nuclear power in-dustry are all Uranium-based. In both nuclear fuel bases, three types of fuel cycles are proposed according to the reprocessing of used nuclear fuel, such as once-though fuel cycle, modified open fuel cycle and fully closed fuel cycle. Because of the rapid growth of energy demand, together with the abundant reserves of Thorium, the importance of Thorium utilization has become increasingly prominent and new Thorium reactors need to be de-veloped.

Th-U fuel cycle has several advan-tages compared to U-Pu fuel cycle [IAEA1450]. The thermal capture cross section of 232Th (7.4 barns) is about 3 times higher than 238U (2.7 barns) while that of 233U (45.76 barns) is much smaller than 239Pu (268 barns). It means that 233U has

higher production and lower con-sumption compared with 239Pu in ther-mal reactors. With the effective fission neutron number higher than 2 in the whole spectrum region, 233U can be bred in both thermal and fast reactors. In addition, the long-lived minor ac-tinide (MA) resulting from fission is much lower in Th-U fuel cycle com-pared with U-Pu fuel cycle. Therefore, 233U has better neutron economy than 239Pu in thermal neutron energy re-gion and Th-U fuel cycle is the only one that can breed in thermal reactors with significantly reduced fissile in-ventory [1].

232U produced via 233U (n, 2n) re-actions has a decay product 208Tl with high gamma radiation (2 ~ 2.6 MeV) [2], which requires shielding in recy-cling and fabrication stages. However, this gamma activity will also allow one to monitor movements of the ma-terial and possible diversion. In addi-tion, thorium and its compounds are very stable and are among the highest known refractories. Thorium oxide is a better thermal conductor than UO2. It has higher melting point, better ra-diation resistance and lower co-effi-cient of thermal expansion [3]. The fission gas release rate of Th-based fuel is smaller than that of U-based fuel when they have comparable ge-ometry, operating conditions, and so on [4–6]. These characteristics allow the thorium-based reactors to be oper-ated in higher temperature and deeper burn-up.

There are also several challenges for Th-U fuel cycle. The daughter products of 232U have strong gamma irradiation, which causes difficul-ties in storage and transport. In the

conversion chain of 232Th to 233U, the intermediate nucleus 233Pa has a 27-day half-life [7] during which 233Pa will capture neutrons and affect the conversion efficiency of 232Th to 233U. Existence of 233Pa also results in a reactivity lag after reactor shutting down and therefore has to be taken into account in reactor design.

Molten Salt ReactorsBeing one of the six candidates of

Gen-IV reactors, Molten Salt Reactor (MSR) is a class of liquid fuel reac-tors, in which nuclear fuel is dissolved in molten fluoride used as the primary coolant (Liquid-fueled Molten Salt Reactor, MSR-LF). Dry reprocess-ing can be applied in MSR system to separate isotopes simultaneously, so that online reprocessing and breeding of nuclear fuel can be achieved. Such a scenario is particularly suitable for the use of Thorium fuel.

Fluoride-cooling High-temperature Reactor (FHR), also known as Solid-fueled Molten Salt Reactor (MSR-SF), is one of the new concepts of MSR. It uses solid fuel assemblies composed of TRISO particles inside graphite substrate, and molten fluoride as coolants. The MSR-SF concept is an integration of proven technologies from other reactor types. It can achieve excellent performance on safety and economy with a high temperature out-put without water-cooling. The MSR-SF has outstanding suitability for the comprehensive utilization of nuclear power based on Hydrogen production and the application of small modular reactor.

Some Physical Issues of the Thorium Molten Salt Reactor Nuclear Energy System



Recently investigations on MSR have drawn fresh attention around the globe, especially in the United States and Asian countries such as Japan, Korea, India, and so on. In the near fu-ture, MSRs (MSR-LF and MSR-SF) is expected to realize comprehensive nu-clear energy applications such as Tho-rium utilization, hydrogen production at high temperature, water-free cool-ing and small modular reactor design, and so on.

Thorium Utilization Based on Molten Salt Reactors

Thorium utilization at MSRs (TMSR) can be realized step by step depending on the fuel cycle modes and the related technology devel-opment adopted on MSRs. First, TMSR-SF can be operated in a once-through fuel cycle for simplicity, which means that the nuclear fuel is used only once and then spent nuclear fuel (SNF) is removed without recy-cling. The convert ratio of Thorium to 233U is not very high. Second, a modified open fuel cycle can be ad-opted at TMSR-SF by online refuel-

ing (pebble circulation) to improve the Thorium utilization and its burn-up (Figure 1).

In principle, Thorium utilization can be realized at a TMSR-LF with the modified open or even full closed fuel cycle due to its unique on-line chemical reprocessing technology (Figure 2). After separation, fission products are geological disposed di-rectly and 233U is recycled, and si-multaneously fertile isotope 232Th or 238U and Minor Actinides (MA) are recovered into fresh MS (Mol-ten Salt) fuel for further burning in TMSR-LF (Figure 2). It can achieve a deeper burn-up as well as a higher BR at TMSR-LF compared with TMSR-SF.

For the TMSR-LF with closed fuel cycle, only small amount of short-lived nuclear waste (fission products and minor heavy metals) is discharged. As can be seen from the comparison of radiotoxicity between TMSRs and PWR, TMSR-SF displays far higher radiotoxicity than liquid TMSR-LF due to shorter operation time and lower burn-up, but lower than traditional PWR.

It should be noted that fuel utiliza-tion, wastes generation together with economical facts, non-proliferation, safety and technology availability play significant roles and all of them should be taken into consideration in comprehensive analysis of vari-ous nuclear fuel cycles. Higher fuel utilization can be attained by using the recycling option, which can only be achieved in liquid reactors (like TMSR-LF).

The TMSR-LF and TMSR-SF have characteristics and applications includ-ing Thorium energy utilization, hydro-gen production at high temperature, water-free cooling, and small modular design. These properties made MSR one of the best approaches to solve en-ergy and environment issues in China. In January 2011, the Chinese Acad-emy of Sciences launched the Stra-tegic Pioneer science and technology Project: Thorium Molten Salt Reactor nuclear energy system (TMSR). The TMSR project intends to construct an TMSR-SF and an TMSR-LF in principle-test scales for experimental investigations, advance R&D abilities in TMSR design and analysis, molten salt fabrication and loop technology, Thorium-based fuel fabrication and reprocessing, and so on. Following a step-by-step approach, the TMSR project has started from principle ex-perimental reactors, and will gradu-ally proceed to engineering demon-stration and industrial promotion. In about 20 years, the TMSR project will strive for realize effective utilization of Thorium-based fuel via R&D of TMSR-LF, accomplish comprehen-sive utilization of high temperature nuclear energy and feasibility of being the primary energy of inland arid area via R&D of TMSR-SF, and establish small modular design and application for both TMSR-SF and TMSR-LF. As shown in Figure 2, we expect that this project will help to solve the energy Figure 1. Material flow of solid and liquid MSR with three types of fuel cycles.



problem in China and realize sustain-able development for a long time.

Challenges of Fuel TechniquesNuclear fuel is the key compo-

nent of a nuclear reactor. The safety and the economy of a nuclear power station depend heavily on the safety and use-method of the nuclear fuel element. The safety of a nuclear fuel element depends not only on the struc-ture and property of the nuclear fuel material itself. It also depends on the compatibilities between nuclear fuel, cladding material, and the coolant. An economic use of nuclear energy means deeper burn-up and less waste dis-posal, both of which can be achieved by elaborate management of the nu-clear fuel element. In a reactor cooled with molten salt, the nuclear fuel el-ement suffers not only high tempera-ture and strong neutron irradiation, but also special chemical environment of molten salt. Therefore the compatibil-ity with molten salt and the cycle fea-sibility of nuclear fuel in the molten salt environment determines the safety and economy of a molten salt reactor.

TRISO (Tri-structural isotropic coated particle) fuel can be a candi-

date fuel for MSR-SF. The TRISO fuel is a kind of all-ceramic fuel with multi-layer coated particles embed-ded in a columnar or spherical graph-ite matrix. The all-ceramic structure made it tolerable for high temperature and most corrosion environments. The TRISO fuel is originally developed for high temperature gas-cooled reac-tors and has been well qualified both in manufacturing and in in-pile opera-tion. For using TRISO fuel in a MSR-SF, care should be taken for soaking and possible corrosion of molten salt to the graphite matrix of the fuel ele-ment. Fluoride salts are the most often chosen coolant due to its low neutron capture cross-section, excellent heat conduction, capacity and low vapor pressure, and so on. The compatibility of fluoride salts with graphite has been proved to be acceptable by ORNL ex-periments conducted before construc-tion of MSRE. Four years safe running of graphite moderator under MSRE environment further demonstrated the compatibility between graphite and fluoride salt. Considering the better thermal conduction and heat capac-ity of molten salt compared to helium gas, future work should concentrate

on fuel designs that can increase fuel power density and burn-up so that the superiority of MSR-SF can be better accommodated. Adequate fuel loading and cycling techniques under molten salt environment should be developed for further improving the economic efficiency.

In TMSR-LF, the fissionable and fertile isotopes are dissolved in a mol-ten fluoride fuel salt, which serves as fuel as well as coolant. The anti-radia-tion damage property together with its in-situ purifying and cycling character of liquid fuel made it ideal for achiev-ing the so-called fully closed nuclear fuel recycle. The LiF-BeF2-ZrF4-UF4 (65-29.1-5-0.9 mole %) quaternary system has been used successfully in the MSRE at ORNL, and the LiF-BeF2-ThF4-UF4 (72-16-12-0.4 mole %) mixture was proposed as a fuel for the molten salt breeder reactor (MSBR) design. Purification tech-niques for producing fluoride mixtures have been developed at ORNL and are adaptable to large-scale produc-tion capabilities. The purpose of salt purification was to eliminate oxides, sulfur, and metal impurities, which could be achieved by treatment of the melted fluoride salt with anhydrous HF, H2, and in some instances, strong metallic reducing agents. It’s expected that complete technical demonstration on in situ fuel treatments, storage, and transportation should be accomplished commonly before the realization of a fully closed fuel cycle.

Fuel Reprocessing TechnologiesIn the traditional U-Pu fuel cycle,

the fissile is 239Pu, its precursor is 239Np; while in the Th-U fuel cycle, the fissile is 233U and its precursor is 233Pa. The half-life of 233Pa (27 days) is 10 times longer than that of 239Np (2.35 days), which means the equilib-rium concentration of 233Pa in reactor

Figure 2. Strategy of TMSR R&D.



is nearly 10 times higher than that of 239Np. If too much 233Pa were accu-mulated in the reactor, the high neu-tron absorption cross-section of 233Pa (~40 barn at 0.0253 eV) will cause sig-nificant consumption of 233Pa as well as neutrons. Hence, the essential issue of chemical reprocessing of Th-U fuel cycle is frequent, even continuous, isolation and extraction of 233Pa from fuel, so as to achieve effective breed-ing of 232Th.

Because the fuel is evenly dis-solved and distributed in the carrier salt (7LiF-BeF2) and cycles as liquid in the reactor system, liquid-fuel MSR is characterized with abilities of onsite reprocessing and recycling. Among all Gen-IV reactors, the TMSR-LF is generally acknowledged as the best candidate to establish Th-U fuel cycle.

The investigation conducted by ORNL [8] shows that, to achieve a high breeding ratio (e.g., BR = 1.07), the processing cycle time (PCT) should be less than 10 days; however, it is very difficult to develop a process handling all elements (Pa, U, Th, FPs, and TRU) with a PCT of 10 days. The French National Center for Scientific Research (CNRS) proposed a simpli-fied process [9] aiming at a self-sus-tainable Th-U cycle (BR = 1.0) with a PCT of 6 months, which will sub-stantially reduce the intensity and dif-ficulty of in situ fuel reprocessing.

However, in TMSR-LF, the enrich-ment of 7Li in LiF should be higher than 99.99% to reduce the neutron loss induced by 6Li; such a highly enriched 7LiF is highly priced with a very limited annual production around the world. Therefore, together with separation of fissile and 233Pa, 7LiF should be isolated and recycled as soon as possible in the fuel reprocess-ing. We proposed a new process as follows: U is separated and recycled in situ, the carrier salt is then separated and recycled. The residue, containing

233Pa, Th, TRU, and FPs is stored until 233Pa decays to 233U, and then U, Th, and TRU are separated orderly. Such a process not only reduces intensity and difficulty of onsite fuel process, but also recycles precious 7LiF in time to reduce the inventory onsite.

Fuel reprocessing technologies can be divided into two categories, pyro-chemical process and aqueous process. Since TMSR-LF requires a timely fuel reprocessing, the irradiated fuel is insufficiently cooled with high radioactivity and poor water-solubil-ity, pyro-chemical process is judged to be the only technology for industrial scale TMSR-LF. For TMSR-LF, the best start-up fuel is 233U. The aqueous process of irradiated Th based on sol-vent extraction could be applied to ob-tain start-up 233U fuel for TMSR-LF.

Challenges of Structural MaterialsThe structural materials of TMSRs

will be subject to the extreme envi-ronments (i.e., high temperature, high neutron doses, and corrosive coolant [10]). Especially in the case of TMSR-LF, the fuel-dissolved fluoride salt in the core will produce a few radioactive or corrosive products (such as Xe, F, I, Cs) under neutron irradiation, which

will poses big challenges for structural materials. Hence, the development of the TMSRs much depends on new high-temperature structural materials which can meet some special require-ments: higher corrosion resistance to molten fluoride salts; higher radiation tolerance; better high-temperature strength and good manufacturability (ability to be deformed, machined, welded, etc.).

Several candidate materials have been widely discussed and suggested for structural applications in advanced fission nuclear systems, such as fer-ritic/martensitic/austenitic (F/M/A) steels, oxide dispersion strengthened (ODS) steels, Ni-base alloys includ-ing ODS Ni-based alloys, ceramics, and ceramic composites [11]. Figure 3 presents their comprehensive perfor-mance evaluation from three aspects (high-temperature strength, corrosion, and radiation resistance) for the appli-cations in TMSR.

The Ni-base alloys are considered to be the primary option of metallic structural materials in TMSR, where the added molybdenum and chromium improve the strength and the oxida-tion resistance, respectively [12]. The Hastelloy N, a Ni-Mo-Cr based al-loy developed at ORNL shows good

Promising materialsOptimal materials

Suboptimal materials

Perfo

rman

ce e

valu

atio

n

F/M steels Austeniticstainless steels

ODS steels Ni-based alloys ODS Ni-basedalloys

Ceramics(SiC,C/C,SiC/SiC)

High-temperature strengthCorrosion resistanceRadiation resistence

F/M/A steels ODS steels Ni-based alloys ODS Ni-basedalloys

Ceramics & ceramiccomposites

Figure 3. Comprehensive performance evaluation for the application prospects of candidate structural materials in TMSR.



strength at 923 K and good chemical compatibility with FLiBe salt during 1.5 years of full power operation of MSRE [8]. Although Hastelloy N was a proven good candidate for TMSR, it has a few limitations that hinder its ap-plication at even higher outlet temper-ature. Such as, the maximum service temperature (e.g., 977 K) will restrict the maximum allowable coolant tem-perature. Subject to helium embrittle-ment will reduce the stress rupture life and the fracture strain. Furthermore, Hastelloy N has not been codified into BPVC section III—Rules for Construction of Nuclear Power Plant Components, particularly not into Subsection NH—Class 1 Components in Elevated Temperature Service. Therefore, better structural materials are required for future TMSR nuclear systems.

F/M/A steels are another group of promising candidate materials for high temperature reactors. They exhibit good strength, and creep resistance to higher temperature (723–923 K) as well as reasonable corrosion/oxida-tion resistance. Similarly, ODS steels have good mechanical properties. They also have good irradiation resis-tance due to the presence of dispersed oxide nano-particles, which can be sunk for irradiation-induced defects [13]. However, their compatibility with coolant may be major issue since the aforementioned iron-based steels are easily subject to corrosion of mol-ten fluoride salts.

It is notable that a kind of Ni-base superalloys (ODS nickel-based alloys) widely used in turbine engine shows good resistance to both radiation dam-age and molten-fluoride-salt corro-sion, inherited from ODS steels and Ni-based alloys, respectively. Further-more, the ODS nickel-based alloys have high strength at 1,273 K, and would be the promising structural ma-terials for TMSR if their medial tem-

perature strength could be improved by the refinement of dispersive oxide nanoparticles and optimization of al-loy compositions [14].

Ceramic and ceramic composites have been proposed for high tem-perature components such as heat exchangers and thermal insulations in the TMSR primary loop. They can also be employed as core components such as control rod cladding, core sup-port plates, reflectors, and fuel clad-ding. The ceramic matrix composites (C/C and SiC/SiC) have better crack resistance, and hence are more favor-able than ceramics as structural mate-rials. C/C composites are well-suited for components that need good ther-mal shock resistance and compatibil-ity with molten salt. However, C/C composites suffer irradiation-induced degradation due to anisotropic dimen-sional changes. SiC/SiC composites have better tolerance to neutron ir-radiation, and keep very good me-chanical strength till the temperature is above 1,375 K. Although SiC has been studied in different chemical en-vironments, the compatibility of SiC with molten salt is still an open ques-tion. There was evidence that stoichio-metric SiC possess very good corro-sion resistance to molten fluoride salts [15]. For the application of SiC/SiC composites in TMSR, further studies are necessary to understand its radia-tion effect (risk of swelling, drop of thermal conductivity and mechanical properties, damage, failure) and cor-rosion behavior in molten salt.

Utilization of High Temperature Nuclear Heat

A typical commercial nuclear reac-tor generates 1,000 MW of electrical energy also produces 2,000 MW of “waste heat” that must be removed from the reactor to keep it from melt-ing down. This is one main reason that

many reactors are sited nearby large bodies of water such as sea or lake, so that they can use amount of water for cooling. TMSRs are designed to provide very high temperature (600 to 1,000°C) heat to enable efficient low cost production of electricity. The nuclear heat of TMSR is delivered at high temperature and low pressure through molten salts as coolant. It is also suitable for non-electric applica-tions at different level heat utilization, including seawater desalination, dis-trict heating, heat for industrial pro-cesses, and hydrogen production [16] (Figure 4).

Hydrogen has a key role in energy utilization as a clean energy carrier and valuable chemical feedstock [17]. Current hydrogen main produce via steam reforming of natural gas, gas-ification processes of coal and petrol reforming. Hydrogen can also be pro-duced by electrolysis of water—but current electrolysis technology is inef-ficient at an overall efficiency of about 25%. Advanced nuclear reactors, such as TMSR, operating at higher temperatures, can produce hydrogen much more efficiently (up to 50%) by high-temperature electrolysis or thermochemical cycles. Moreover, the coolant with molten salts can provide a better solution for heat transfer from nuclear reactor to hydrogen produc-tion plant. They are very stable chemi-cal compounds, and have a very low vapor pressure and good heat transfer properties.

There are two main categories of hydrogen production technologies to meet with TMSR. The first important technique is High Temperature Stream Electrolysis (HTSE). The basic theory of HTSE is to split water into hydro-gen and oxygen through electrolysis at high temperatures using Solid Oxide Electrolysis Cells (SOEC). Compared with conventional low-temperature (<100°C) electrolysis, high tempera-



ture electrolysis increases the perfor-mance and the electricity-to-hydrogen efficiency by minimizing the Gibbs free energy of the reaction. HTSE uses heat from the reactor to replace some of the premium electricity required in alkaline electrolyzers.

Thermochemical (TC) production of hydrogen is to split water into hy-drogen and oxygen through a series of chemical reactions at high tem-peratures (450–1,000°C in nuclear hydrogen). More than 100 different TC cycles can be used in hydrogen production by nuclear energy. Ura-nium thermochemical cycle (UTC) is used at temperatures well below 700°C to produce hydrogen, which was investigated by Oak Ridge Na-tional Laboratory. Only three steps at relatively low temperatures and pressures are needed in the whole process. The operating conditions of UTC are mild and most of the steps are commercially used in uranium processing industry. The overall fea-sibility of the UTC is still in its early conceptual phase, and only has been demonstrated using common labora-tory equipment. Additional analysis including efficiencies, economics,

and experimental work is required before engineering viability [18].

Methanol is an important chemi-cal for gasoline production and olefine production, which can be produced from hydrogen. The methanol econ-omy, advocated by George Olah, win-ner of the 1994 Nobel Prize in chem-istry, is a suggestion that methanol can replaces fossil fuels as a means of energy storage, transportation fuel, and raw material for synthetic hydro-carbons and their products [19]. It can also be readily transformed by dehy-dration into dimethyl ether (DME), or by Methanol-to-Gasoline (MTG) process, which converts methanol to high quality clean gasoline. Except for the Heat-Hydrogen-Methanol-Gas-oline route, co-electrolysis of CO2/H2O with SOEC cell also provides a Heat-CO2/H2O-Syngas-Methanol-Gasoline route. A massive quantity of hydrogen production from nuclear energy provides a cheap and large-scale solution to fit the demand of the methanol economy.

Summary and OutlookIn summary, the purpose of the

TMSR project is to achieve a sus-

tained thorium-based nuclear system with high temperature output, maxi-mized thorium utilization, and mini-mized radiotoxicity of spent nuclear fuel. Since there are still several chal-lenges for Th-U fuel cycle and molten salt reactor development, it is reason-able to expect that this TMSR project will shed light on the energy problem in China and realize sustainable devel-opment for a long time.

AcknowledgmentsThis work is supported by the Tho-

rium Molten Salt Reactor Nuclear En-ergy System under the Strategic Pio-neer Sci. & Tech. Project of Chinese Academy of Sciences under contracts No. XDA02000000.

The authors appreciate the valuable suggestions and comments from many other experts including Dr. Qingnuan Li, Dr. Zhiyong Zhu, Dr. Ping Huai, Dr. Jianqiang Wang, Dr. Jingen Chen and Dr. Wei Guo.

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Figure 4. Nuclear heat of MSR for many applications at different tempera-ture ranges.



8. M. W. Rosenthal et al., ORNL-4812 (Oak Ridge National Laboratory), (1972) 1–416.

9. L. Mathieu, D. Heuer, A. Nuttin, F. Perdu, A. Billebaud, R. Brissot, C. Le Brun, E. Liatard, J.M. Loi-seaux, O. Meplan, E. Merle-Lucotte, S. David, C. Garzenne, and D. Lecar-pentier. Thorium molten salt reactor: from high breeding to simplified re-processing. GLOBAL 2003—Nuclear Science and Technology: Meeting the Global Industrial and R&D Chal-lenges of the 21st Century, New Or-leans, LA, USA.

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16. Non-electric applications of nuclear power: seawater desalination, hydro-gen production, and other industrial applications; Proceedings of an in-ternational conference, Oarai, Japan, 2007.

17. X. X. Yan et al., Nuclear hydrogen production handbook (CRC Press, Boca Raton, FL, 2011).

18. C. Forsberg et al., A uranium thermo-chemical cycle for hydrogen produc-tion, Fourth Information Exchange Meeting Oakbrook, Illinois, USA, 2009.

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CAS Center for Excellence in TMSR Energy Systems

Shanghai Institute of Applied Physics, Chinese Academy of Sciences,

Shanghai, China

Xiangzhou Cai

zhimin Dai

hongjie Xu

Filler?

meeting reports


From 12 to 17 May 2013 the Fourth International Particle Accelerator Con-ference (IPAC’13) was held in Shang-hai, jointly hosted by the Shanghai Institute of Applied Physics (SINAP) and the Institute of High Energy Phys-ics (IHEP), both of which are affiliated with the Chinese Academy of Sciences (CAS).

IPAC is the largest academic con-ference in the international accelerator community, following a 3-year cycle among the three regions (Asia, Eu-rope, and North America). This is the first time IPAC was held in China. The main organizers were Zhentang Zhao (OC Chair) and Zhimin Dai (LOC Chair) from SINAP and Ch-uang Zhang (SPC Chair) and Qing Qin (LOC Co-Chair) from IHEP. Over 1,300 accelerator scientists, engineers, and industrial vendors from 33 coun-tries have participated in the event. The conference has received 1,300 submitted papers and held 96 oral pre-sentations, as well as attracting a total of 84 vendors.

IPAC’13 aimed to reflect the lat-est trends and dynamics in the in-

ternational particle accelerator field through its well-structured scientific program, which incorporates plenary invited oral presentations, invited oral presentations, contributed oral presen-tations, and poster sessions. It has re-ported most recent advances and inno-vations in particle accelerator physics, technology, research and applications in industry, covering a wide spectrum of subjects such as circular and linear colliders, synchrotron light sources and FELs, particle sources and alter-native accelerator techniques, had-ron accelerators, beam dynamics and electromagnetic fields, beam instru-mentation and feedback, accelerator technology and applications, and tech-nology transfer and industrialization.

There were eight plenary invited oral presentations featuring the most relevant and prevailing topics in accel-erator science. Wenlong Zhan (IMP), academician and Vice President of the CAS, spoke on China’s ADS pro-gram and key technology R&D at the opening ceremony (Figure 1). Mi-chael A. Plum (ORNL) discussed the challenges facing high power proton

accelerators. Six other presentations include “The First Years of LHC Op-eration for Luminosity Production” by M. Lamont (CERN); “Review of Laser Wakefield Accelerators” by V. Malka (LOA); “Brightness and Coherence in Synchrotron Radiation and FELs” by Z. Huang (SLAC); “An Overview of Light Source Development in Asia” by D. Wang (SINAP); “Recent LHC Physics Results and their Impact on Future HEP Accelerator Programme” by S. Bertolucci (CERN); and “Recent Progress of Neutrino Experiments and Requirement for Accelerators” by Y. F. Wang (IHEP).

Three ACFA/IPAC’13 Accelerator Prizes were awarded at the confer-ence. Shouxian Fang (research fel-low at IHEP, China) won the prize for outstanding work in the accelerator field. Professor Fang has contributed to accelerator physics and technology throughout his whole scientific career. He in particular led the team construct-ing the Beijing Electron-Positron Col-lider (BEPC), the first high energy accelerator in China. Dr. Michael Bor-land (Argonne National Laboratory,

The Fourth International Particle Accelerator Conference

Figure 1. The opening ceremony of IPAC’13 at Shanghai International Convention Center.

meeting reports


USA) and Dr. Hiroshi Imao (RIKEN, Japan) are the two other recipients of the award due to their significant achievement and/or an original contri-bution to the accelerator field. Dr. Bor-land has created the ELEGANT pro-gram and its SDDS platform that are widely applied in design, simulation, and analysis of circular accelerators, ERLs and FELs. Dr. Imao is awarded for the realization of the next-genera-tion charge-state stripper using recir-culating helium gas. Each of the three laureates briefed about their work at the Awards Session.

In order to encourage the participa-tion of young scientists, IPAC’13 set up a special poster session for young scientists, which attracted 112 stu-dents’ contributions from around the world, presenting their research find-ings in accelerator technology and in-

dustrial applications. Two best student poster prizes were awarded.

IPAC’13 provided a great oppor-tunity for the international accelerator community to get informed of recent development of particle accelera-tor science and technology in China. More than 160 delegates visited the Shanghai Light Source (SSRF), an affiliation to SINAP, after the confer-ence.

The conference was held at Shang-hai International Convention Center, a venue that guarantees success of a technical conference while offering exceptional cultural experience and superb scenic beauty. Living right across Shanghai’s iconic bund, par-ticipants savored the local charms and flavors while enjoying the mixing and mingling with friends and colleagues through the conference’s rich social

program, including a traditional Chi-nese calligraphy performance.

The conference is supported by CAS, National Natural Science Foun-dation of China, Science and Technol-ogy Commission of Shanghai, Asian Committee for Future Accelerators (ACFA), American Physical Society (APS-DPB), European Physical So-ciety (EPS-AG), and the International Union of Pure and Applied Physics Federation (IUPAP).

The Fifth International Particle Ac-celerator Conference will be held in Dresten, Germany during 15–20 June of 2014.

Zhentang Zhao

Shanghai Institute of Applied Physics, Chinese Academy of Sciences

The 10th Latin American Sym-posium on Nuclear Physics and Ap-plications (X-LASNPA) was held on 1–6 December 2013 at the Facultad de Ingeniería in Montevideo, Uruguay (Figure 1). The symposium brought together about 130 scientists and stu-dents from over 26 different countries

and was an opportunity to review the forefront research in nuclear science and strengthen the links of and with the Latin American nuclear physics community. The scientific program included plenary and parallel sessions as well as a poster session with about 50 contributions. The meeting was

preceded by the School on Medical Physics, which was held on 29–30 November 2013, and attracted about 30 participants.

This is the tenth symposium in a se-ries that was previously held in Vene-zuela (1995, 1997), Colombia (1999), Mexico (2001), Brazil (2003), Argen-tina (2005), Peru (2007), Chile (2009), and Ecuador (2011). Traditionally, the purpose of these symposia is the dis-semination of major theoretical and experimental advances in nuclear science, with emphasis on research topics carried out by Latin American groups or in collaborations involving institutions from Latin America. This includes fundamental nuclear science and also numerous contributions from applications of the field, which are important due to their broad impact in

10th Latin American Symposium on Nuclear Physics and Applications

Figure 1. Group photo from the 10th Latin American Symposium on Nuclear Physics and Applications.

meeting reports


the region and on society. The topics covered at the meeting in Montevideo included: nuclear applications in med-icine, energy, space and national secu-rity; nuclear and particle astrophysics; tests of fundamental symmetries and properties of neutrinos; hadron struc-ture; nuclear reactions and phases of nuclear matter; nuclear structure and spectroscopy; and new facilities and instrumentation.

The symposium was also the oc-casion for a meeting of the Latin American Association of Nuclear Physics and Applications (ALAFNA), which was created in Santiago, Chile in 2009. The main objectives of ALAFNA are the strengthening of the Latin American community involved in pure and applied nuclear research; the sensitization of the general public to nuclear science and education of

young scientists; and the evaluation and assessments of nuclear science developments in Latin America.

It has also become a tradition in these symposia to acknowledge dis-tinguished members of the commu-nity. This time the awards were attrib-uted during the conference dinner to Dr. Giuseppe Viesti from the Instituto Nazionale di Fisica Nucleare, Padova, Italy and to Prof. Norberto H. Medina from University of Sao Paulo, Brazil, for their careers and for their strong in-volvement in the promotion of nuclear science in Latin America (Figure 2).

It was announced that the next XI-LASNPA meeting will be held by the end of 2015 in Medellin, Colombia. This will continue fostering nuclear science throughout Latin America and will offer new opportunities to cross-fertilize ideas between the Latin

American nuclear physics community and other groups world-wide.

oscar naviliat-cuncic

Michigan State University, East Lansing, Michigan, USA

Figure 2. G. Viesti from INFN, Pado-va, Italy and N. H. Medina from Uni-versity of Sao Paulo, Brazil received the award distributed by ALAFNA. (Photo courtesy A. Lépine-Szily and D. A. Torres Galindo.)

Shape-Phase Transitions in Nuclei: Spreading the Wings

The 7th Workshop on Shape-Phase Transitions and Critical Point Phenomena in Nuclei was held in Se-ville, Spain, from 10–13 March 2014. This is the seventh workshop in this unique series, following previous ones in Berkeley (2004), Camerino (2005), Sofia (2006), Athens (2007), Istanbul (2009), and Darmstadt (2012). Participants came from more than 20 countries, with an interesting mixture of senior and young research-

ers. This series of workshops has a unique format: each of the sessions is devoted to a topic of particular inter-est and is coordinated by a convener who selects a single featured speaker, along with a few brief presentations and extended periods of discussion, giving ample time for scientific inter-actions and give and take.

The first entry in the series, in Berkeley, focused largely on the then new topic of Quantum Phase

Transitions (QPT) in nuclei in the form of simple theoretical descrip-tions called X(5) and E(5). Since then the subject matter has broadened considerably, both within nuclear physics and beyond—to a stagger-ing variety of transitional behaviors and the (largely) symmetry-based ap-proaches to understanding it. Exten-sive discussions, for example, looked at partial and quasi symmetries (sym-metries where some of the properties

meeting reports


of a parent symmetry persist while others do not, or where symmetries persist just for a subset of the sys-tem states), point group symmetries and the way of constructing Nuclear Physics Hamiltonians subject to cer-tain point groups, treatment of shape phase transitions within geometric models, proton-neutron symmetries and mixed symmetrical states, the appearance of quantum phase transi-tions in excited states, structural evo-lution in odd-A nuclei (Bose-Fermi symmetries and shape transitions), and the microscopic origins of these manifestations of collective behavior.

Although originally centered in nuclear physics, increasingly, in these workshops, discussions of re-

lated topics in other physical systems are becoming an important theme. Thus, there were sessions devoted, for example, to atomic and molecular systems, coupled systems including either different kinds of bosons or bo-sons and fermions, phase transitions in insulators and spin systems, in-cluding topological and Dicke phase transitions. Another session focused, not on spatial geometry, but on pat-terns in time series—with biological applications, such as analyses of such series to provide “early warning” signals of criticality and correlated behavior in complex biological and geological entities. Theoretical and mathematical tools (mostly symme-try-based) developed for the study

Figure 1. The sessions took place at the main building of University of Seville, which was originally the tobacco factory where the famous Carmen in the opera Carmen by Merimee was working. The photo shows some of the participants in one of the main stairs of the building.

of nuclei have proved to be useful in other systems, and vice versa. This is a paradigmatic example of a cross-fertilization of ideas, Nuclear Phys-ics ideas about QPTs influenced other areas and now vice versa as we saw. This is a two-way street that benefits everyone. Meetings in this series have evolved to acquire an interest-ing multidisciplinary character. In this sense, one of the lecturers coined the phrase “we are spreading our wings” that we borrowed for the title.

An overarching theme in much of the discussions was the emergence of extremely simple and regular be-havior in complex systems, ways of modeling it, and ways of understand-ing its microscopic origins.

The venue of this international workshop on Shape-Phase Transi-tions and Critical Phenomena in Nu-clei was the Great Hall (Aula Magna) of the Philology Faculty, located at the main building of the University of Seville (Figure 1), at the very heart of the city. It provided the appropriate environment for the meeting. It is not exactly U-shape, as it was the semi-nar room in previous editions, but it allowed us equally to have vivid and fruitful discussions.

A very well-received break from the sessions was an impressive pri-vate tour of the amazing Reales Al-cázares in Seville and a wonderful riverside conference dinner.

The next (8th) workshop in this series will be held in Prague, Czech Republic, in 2016, organized by Pavel Cejnar.

clara e. alonso and Jose M. arias

University of Seville, Spain,

Francisco PéreZ-Bernal and José e. garcía-raMos

University of Huelva, Spain

news and views


A scientific program named SEA-STAR aiming at the investigation of shell evolution and the measurement of new 2+ state energies in unstable nuclei via in-beam gamma-ray spec-troscopy has been initiated at the Radioactive Isotope Beam Facility (RIBF) of the RIKEN Nishina Center. With SEASTAR, the RIBF pursues a new approach, allowing for project-type experimental “proposals for sci-entific program” that aim for survey-ing a broad range of exotic nuclei for specific quantities with a dedicated detector setup. SEASTAR plans to exploit the opportunities offered by producing the world’s most intense intermediate energy radioactive iso-tope beams coupled with the high-ef-ficiency DALI2 gamma-ray spectrom-eter [1] and the new MINOS thick hydrogen target and vertex tracker [2] (Figure 1).

In-beam gamma-ray spectroscopy with fast exotic nuclei has been dem-onstrated to be one of the most power-ful tools to investigate nuclear struc-ture away from stability following secondary reactions. Employing this technique at the RIBF, new nuclear shell structure effects have been un-veiled in very exotic nuclei in recent years [3]. In order to increase the lu-minosity of such experiments and to minimize the Doppler broadening introduced by beam velocities above 50% of the speed of light, an innova-tive combination of a thick liquid hy-drogen target and a vertex tracker has been developed at CEA Saclay.

The SEASTAR scientific program covers the most neutron-rich Ar (Z = 18) to Zr (Z = 40) isotopes that can be accessed worldwide from in-beam gamma spectroscopy today (Figure 2) and will be organized in experimental campaigns over a period of several years. The collaboration is open to every researcher interested in the sci-entific program. By-product data will be provided to the collaboration after every campaign. Composed already of more than one hundred research-ers from 25 institutes worldwide, the collaboration is poised for its first campaign this spring aiming for spec-troscopy around the doubly-magic 78Ni. Further details on the physics case as well as the detector equipment utilized in this project and its organi-zational structure can be found under Ref. [4]. Any interested scientist can join the project by sending an e-mail to [email protected].

References1. T. Takeuchi et al., submitted to Nucl.

Instr. Meth. Res. A (2014). 2. A. Obertelli et al., Eur. Phys. J. A 50

(2014) 8. 3. D. Steppenbeck et al., Nature 502

(2013) 207; P. Doornenbal et al., Phys. Rev. Lett. 111 (2013) 212502.

4. http://www.nishina.riken.jp/collaboration/ SUNFLOWER/experiment/seastar/index.html

P. Doornenbal RIKEN Nishina Center

a. obertelli CEA Saclay

Spokespersons of the SEASTAR collaboration

Shell Evolution and Search for Two-Plus Energies at RIBF (SEASTAR): A RIKEN Scientific Program at the Radioactive Isotope Beam Factory

Figure 1. View of MINOS inside DALI2.

Figure 2. Present SEASTAR physics case.

news and views


Thanks to the joint efforts and built on the existing collaboration of many nuclear physicists in both China and the United States, the China-U.S. The-ory Institute for Physics with Exotic Nuclei (CUSTIPEN) was officially established in May 2013 at Peking University in Beijing. The funding for CUSTIPEN is currently provided by the U.S. Department of Energy (DOE), Peking University and the Institute of Modern Physics, Chinese Academy of Science. As a center for innovative research, CUSTIPEN will provide a unique platform for Chi-nese and American collaborators to combine their vast pool of talent and expertise as well as cutting-edge com-puting resources and theoretical tools to tackle some of the most critical and complex scientific issues raised by the latest experiments conducted at the advanced rare isotope beam facilities around the world.

Nuclear theory plays an extremely important role in the study of rare iso-topes. It poses scientific questions that lead to the construction and operation of new facilities, guides the research programs, and provides frameworks to understand new phenomena ob-served in experiments at these facili-ties. However, the complexity of the new problems and the challenges to effectively solve them timely requires varied expertise, theoretical tools, computing resources, and funding that are hard to find in a single country. The role of international collabora-tions in studying the physics of ex-otic nuclei has thus never been more important. Two outstanding examples are the Japan-U.S. Theory Institute for Physics with Exotic Nuclei (JUSTI-PEN) and the France–U.S. counter-part FUSTIPEN. These two institutes facilitate collaboration of U.S. scien-tists with their Japanese and French

counterparts in the pursuit of a basic understanding of exotic nuclei and their role in astrophysics and else-where. CUSTIPEN was established following these successful examples. As both China and the United States continue to develop more advanced rare isotope beam capabilities and re-lated science programs, there are un-precedentedly strong reasons for more close collaborations between the two countries in radioactive beam science. Both China and the United States have been investing heavily in ex-periments at their respective radioac-tive beam facilities that need stronger theoretical supports. Both countries are world leaders in supercomputers providing a truly unique opportunity for the most sophisticated large-scale nuclear many-body calculations nec-essary for a thorough understanding of exotic nuclei and reactions induced by them. As more U.S.-trained Ph.Ds

CUSTIPEN: China-U.S. Theory Institute for Physics with Exotic Nuclei

Figure 1. Participants of the CUSTIPEN opening ceremony and the CUSTIPEN Workshop on Properties of Exotic Nuclei, Neutron-Rich Nucleonic Matter and Their Astrophysical Impacts.

news and views


and postdocs are returning to China to take faculty and leadership positions at top research universities and na-tional laboratories, while a large num-ber of high quality Chinese graduate students and postdocs continue to go to the United States, CUSTIPEN will further enhance workforce mobility between the two countries and thus help train the next generation world-class nuclear scientists for both China and the United States. Recognizing the need and unique potential for more productive collaborations benefiting both countries, the U.S. Department of Energy (DOE) decided recently to support CUSTIPEN as one of its in-ternational collaborative programs in nuclear theory. Simultaneously, CUSTIPEN also received strong sup-port from many institutions in China.

CUSTIPEN is located at Peking University in China. It supports both theorist–theorist and experimental-ist–theorist collaborations involving faculty members, research scientists, postdocs, and students from any Chi-nese and American research institu-tion. Its operation is managed by a governing board consists of the fol-lowing members:

Chinese Members of the CUSTIPEN Governing Board:

• Yugang Ma (Shanghai Institute of Applied Physics)

• Zhongzhou Ren (Nanjing Uni-versity)

• Furong Xu (Managing Director, Peking University)

• Yanlin Ye (Co-Director, Peking University)

• Wenlong Zhan (Chinese Acad-emy of Science)

• Huanqiao Zhang (China Institute of Atomic Energy)

• Yuhu Zhang (Institute of Modern Physics, CAS)

• Shan-gui Zhou (Institute of The-oretical Physics, CAS)

U.S. Members of the CUSTIPEN Governing Board:

• P. Danielewicz (Co-Director, Michigan State University)

• Bao-An Li (Principal Investi-gator, Texas A&M University–Commerce)

• W. Nazarewicz (University of Tennessee and ORNL)

• J. Piekarewicz (Florida State Uni- versity)

• B. Sherrill (Michigan State Uni-versity)

The opening ceremony and CUSTI-PEN’s first workshop on Properties of Exotic Nuclei, Neutron-Rich Nucle-onic Matter and Their Astrophysical Impacts was held in Beijing, 8–9 May 2013. As shown in Figure 1, over 60 Chinese and American nuclear physi-cists attended the events and discussed plans of more close collaborations in order to make good use of the oppor-tunities provided by the CUSTIPEN. More information about CUSTIPEN can be found at http://CUSTIPEN.PKU.EDU.CN.

Bao-an Li

Texas A&M University–Commerce, Commerce, Texas, USA

Furong Xu

Peking University, China

Filler?

obituary


TRIUMF lost a dear member of its family when Erich Vogt, its co-founder and visionary leader, passed away peacefully in Vancouver General Hos-pital on 19 February 2014. Erich Vogt and TRIUMF have been inseparable since 1968 when the Canadian govern-ment approved the construction of the 500 MeV cyclotron. Erich’s philoso-phy was that cooperation would pro-vide the way for Canadian Scientists to play leadership roles on the world stage of nuclear and particle physics. That defined his management style and the work ethics for the laboratory.

Erich was born in the very center of Canada and received his undergradu-ate education at the University of Manitoba, moving to Princeton for his Ph.D. in nuclear reaction theory under Eugene Wigner (1955). He worked for 10 years at the Chalk River Labora-tory, which was then one of the pre-mier nuclear physics laboratories in the world. Erich joined the physics de-partment of the University of British Columbia in 1965. He and John War-ren formed a consortium of the three BC universities to promote and build TRIUMF. TRIUMF was approved in 1968 and the first beam obtained in 1974. By the mid to late 1970s a broad science program was in full swing at the TRIUMF cyclotron. Strong col-

laborations were built with Japan, with Japanese physicists providing a muon beam-line. The collaboration with Israel enhanced the proton and pion nuclear program and collabora-tion with U.K. groups provided the best study on nucleon-nucleon phase shifts in the 200–500 MeV region. He brought in key players to expand the science program.

Erich, TRIUMF’s director from 1981 to 1994, foresaw the importance of broadening the science program beyond nuclear and particle phys-ics, and supported a material science and chemistry effort using muons as well as investing in a radiochemistry program to support medical imag-ing diagnostics. He also envisaged the importance of developing small cyclotrons radiotracer production in a hospital environment and initiated transfer of cyclotron technology from TRIUMF to a local manufacturer. In parallel a strong industry–laboratory collaboration with NORDION was established on the TRIUMF site to produce and deliver more than 50,000 patient doses a week of radioisotopes worldwide.

By the mid 1980s,TRIUMF was well established and regarded for its scientific output. However, Erich had a much more ambitious plan with KAON. Erich became a travel-ing salesman and advocate to rally the world to his cause, convincing Europe, the United States, and Japan that everyone should join KAON. Erich encouraged the TRIUMF staff to take a more visible role in experiments abroad (e.g., SLAC, HERA, LEP, BNL, KEK) bringing TRIUMF into the big league of nuclear and particle physics research. After the decision of the Canadian government to not pro-

ceed with KAON, Canada was able to join the LHC program, push the rare kaon decay program at BNL, establish a neutrino group, and support the Ca-nadian physics community to access foreign facilities most effectively.

Erich served on numerous advisory and review committees for nuclear laboratories and physics departments. He was co-editor with J. Negele (MIT) of 27 volumes of Advances in Nuclear Physics, which were regarded as the reference publications for training nuclear scientists. He served on the IUPAP Nuclear Physics commission (C12) for three terms, one as chair. He also represented the C12 commission on the joint IUPAP–IUPAC working group on the identification of new ele-ments.

Erich was a fantastic educator and motivator. More than 5,000 students enjoyed the three 8:30 a.m. Phys101 lectures he gave each week until he turned 80. Erich was also a people per-son and took great pleasure at greet-ing everyone at TRIUMF in his (her) mother tongue. He would call you on your birthday, and he would visit the counting rooms at 7 a.m. to keep in touch with the scientists and their progress.

Perhaps the recent announcement of a federal government funding com-mitment for TRIUMF for the period 2015–2020, a full year ahead of ex-pectation, was such a recognition of his vision for the lab that he let go knowing TRIUMF would continue to prosper.

Thank you Erich for the many les-sons, and for your trust.

Jean-Michel Poutissou and ewart BlackMore

Senior scientists Emeriti, TRIUMF

In Memoriam: Erich Vogt (1929–2014)

Erich Vogt

calendar


2014June 30–July 4

Darmstadt, Germany. Direct Re-actions with Exotic Beams DREB2014

https://indico.gsi.de/conferenceDisplay.py?confId=2347

July 7–11Debrecen, Hungary. Nuclei in the

Cosmos NIC14http://www.nic2014.org/

July 20–25Vancouver, Canada. Nuclear

Structure 2014http://ns2014.triumf.ca/

August 24–28Nizhny Novgorod, Russia. EC-

RIS-2014http://ecris14.iapras.ru/

August 31–September 7Zakopane, Poland. Zakopane

Conference on Nuclear Physics “Ex-tremes of the Nuclear Landscape”

http://zakopane2014.ifj.edu.pl/

September 8–13Kaliningrad, Russia. VII Inter-

national Symposium on Exotic Nu-clei (EXON-2014)

http://exon2014.jinr.ru/

September 14–18Monterey, California, USA. 3rd

International Beam Instrumenta-tion Conference, IBIC 2014

https://conf-slac.stanford.edu/ibic-2014/

September 15–19Chicago, IL, USA. Type Ia Su-

pernovae: Progenitors, Explosions, and Cosmology

https://kicp-workshops.uchicago.edu/sn2014/index.php

September 15–19Wien, Austria. EXA2014 Inter-

national Conference on Exotic At-oms and Related Topics

http://www.oeaw.ac.at/smi/research/talks-events/exotic-atoms/exa-14/

September 15–October 10Stockholm, Sweden. Computa-

tional Challenges in Nuclear and Many-Body Physics

http://agenda.albanova.se/conferenceDisplay.py?confId=3987

September 16–24Erice, Italy. Nuclei in the Labo-

ratory and in the Cosmoshttp://crunch.ikp.physik.tu-

darmstadt.de/erice/2014/index.php

September 21–26Canberra, Australia. 5th Joint

International Conference on Hyper-fine Interactions and Symposium on Nuclear Quadrupole Interactions (HFI/NQI 2014)

http://www.hfinqi.consec.com.au/

September 29–October 3St. Goar, Germany. 9th Interna-

tional Conference on Nuclear Phys-ics at Storage Rings STORI’14

http://web-docs.gsi.de/~stori14/

October 13–17Worms, Germany. EPS Nuclear

Physics Divisional Conference “Sci-ence and Technology for FAIR 2014”

https://indico.gsi.de/conferenceDisplay.py?confId=2443

November 3–8Ho Chi Minh City, Vietnam. In-

ternational Symposium on Physics of Unstable Nuclei 2014 (ISPUN14)

http://www.inst.gov.vn/ispun14/

2015May 25–29

Urabandai, Fukushima, Japan. 5th International Conference on the Chemistry and Physics of the Trans-actinide Elements (TAN 15)

http://asrc.jaea.go.jp/conference/TAN15/

June 7–12Hohenroda, Germany. EU-

RORIB2015http://www.gsi.de/eurorib-2015

June 21–26Catania, Italy. 12th International

Conference on Nucleus-Nucleus Collisions (NN2015)

http://www.lns.infn.it/link/nn2015

August 3–September 4 Groningen, The Netherlands.

European Nuclear Physics Confer-ence (EuNPC 2015)

http://www.eunpc2015.org/

August 31–September 4Groningen, The Netherlands.

European Nuclear Physics Confer-ence (EuNPC 2015)

http://www.eunpc2015.org/

September 6–13Piaski, Poland. 34th Mazur-

ian Lakes Conference on Physics “Frontiers in Nuclear Physics”

http://www.mazurian.fuw.edu.pl/

September 14–19Kraków, Poland. 5th Interna-

tional Conference on “Collective Motion in Nuclei under Extreme Conditions” (COMEX5)

http://comex5.ifj.edu.pl/

More information available in the Calendar of Events on the NuPECC website: http://www.nupecc.org/

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